Friday, October 31, 2008

Elvis has Left the Building

I was just informed that the indexer is done and the last piece of the book is at the printers. I think this has to count as being "officially" done, although it won't feel real until I have a copy in my hand.

By the way, the final cover was a grapefruit, and it looks good and matches well with the other books in the series that will be coming out, which all have different kinds of citrus fruits. Again, please don't ask me why we have citrus fruits, I don't know any more than I know why O'Reilly has woodcuts on theirs. It looks good, and that's all that matters.

Updated SQLitePersistence

As I think I mentioned earlier, Marcel Molina is doing some great work adding Ruby ActiveRecord style associations and also refactoring some of my code to make it much cleaner and neater.

Today, I did a little surgery of my own, albeit minor outpatient surgery. I added a bunch of methods to the database instance manager to allow greater control over database configuration, allowing you to specify such things as the autovacuum level, cache size, and the like.

Even if you don't have an interest in using SQLitePersistentObjects, if you use SQLite for either iPhone or Mac/Cocoa applications, it's probably worth your time to take a look at the SQLiteInstanceManager class in the project. It stands on its own and can be used without the rest of the package and it makes managing your database a heck of a lot easier. Just drop it into your project, grab a reference to the sharedManager, and start working with it - no need to create or open the database, or specify a file location or anything.

And, when you realize how nice it is not to have to write code to do any of that, maybe you'll become interested in checking out the rest of SQLitePersistentObjects.

Note: Anybody out there who has successfully used SQLitePersistentObjects for a delivered application, please let me know, and also let me know of any problems you encountered along the way.

Thursday, October 30, 2008

Some More Open Source

This time, it's not me offloading my old source code on you, though. It's an iPhone app by Jonathan George called Packlog, which is a client for updating 37Signal's BackPack Journal.

You can find the source code (released under the very lenient MIT license) right here.

Thanks, Jonathan!

Wednesday, October 29, 2008

Speaking of Wil Shipley

Since I mentioned Wil Shipley, I thought I'd post a link to his excellent C4 presentation. Here it is. If you're an indie developer, and didn't go to C4, watch this video.


I didn't run the press release yesterday, but apparently other bloggers took the bait. Basically, this company called "oDesk" (which I had never heard of before receiving their press release) claims that the demand for iPhone Developers is up 500% in six months.

Of course, this is based on "internal data" with a sampling size that is admittedly too small to be valid. Besides, six months ago, the SDK wasn't even stable and you couldn't distribute apps yet. It was the era of first-wavers, and with the exception of a few large companies that Apple got on board with them, most of the first-wavers were individuals and small Mac development shops.

Now with huge App Store success stories running rampant and general consensus being that the App Store is a runaway success (albeit with few hiccups along the way), of course everyone wants in! There's gold in them thar hills! It's no longer risky to jump into the fray. Those of us who saw the opportunity for what it is from the start and jumped in with both feet (in my case, turning my back on a client-base I had been developing for almost a decade in the process) got a head start because we took a chance. We trusted our judgment and jumped.

Now, all this press release really says is that some johnny-com-lately company has realized we were right and wants to cash-in on that missed opportunity. And though the numbers look good on the surface (or would if they were statistically valid), crap like this actually sucks for our platform. This is the kind of things that college and high-school students read and say "Oh, I want to be an iPhone developer". And, of course, most of them don't want to be an iPhone developer because they love tinkering or programming or problem solving. They want to be an iPhone developer because they envision themselves making big bucks with little effort, spending their days sitting in hot tubs with playmates, driving expensive cars, and otherwise living the high life.

(Just for the record, that is not the life of any iPhone developer I know, except maybe Wil Shipley, but I only know him by reputation.)

It's like those Microsoft Certified Training programs with the radio ads that promise to take somebody who doesn't know jack shit about computers and in six weeks turn them into a "certified" guru who can handle any job that needs to be handled.All this shit floods the market with people who don't know their ass from a hole in the ground. It drives up rates in the short term and causes them to crash in the long run, and it makes it miserably hard for companies to find developers who knows what they're doing unless they happen to already have somebody who's technically knowledgeable about the SDK who can weed out the chaff.

I guess it's inevitable. Success attracts. And, in the long run, it's probably good for the platform, but there's going to be some rough times ahead as a result. I wish success only attracted the right people and for the right reasons.

Better Template

Hello again.

I'm in desperate need of a better template for this blog - one that has good support for code snippets and preferably uses flexible width rather than just floating in the middle of the screen when the viewer has a large monitor (and these days, what developer doesn't?).

My searches for blogspot/blogger templates mostly brings up templates that have different visual elements, fonts, and colors, but the same basic layout as the default templates. If anyone knows of a good template, I'd really appreciate a heads up. I don't mind tweaking the code, but I don't have time write one from scratch. My Web-Fu is rusty and weak.

I've got a couple of more full-fledged tutorial I'm interested in doing, but it's just too painful with this template.


Tuesday, October 28, 2008

CGAffineTransform 1.1 - A little more

I mentioned "shear" in the last article, but I didn't show you how to use transformations to shear a view. When you "shear" a rectangle, you turn it into a parallelogram. Apple doesn't provide a function to do this, but you can do so much with transformation matrices beyond what they've given you functions to do. Here is an example of one. The "shear" matrices look like this:

X Shear

| 1 0 0 |
|SHx 1 0 |
| 0 0 1 |

Y Shear

| 1 ShY 0 |
| 0 1 0 |
| 0 0 1 |

So... we can make our own CGAffineTransformShear() functions. Here we go, fasten your seatbelts:


#import <UIKit/UIKit.h>
#import <CoreGraphics/CoreGraphics.h>

CGAffineTransform CGAffineTransformMakeXShear(CGFloat proportion);
CGAffineTransform CGAffineTransformXShear(CGAffineTransform src, CGFloat proportion);
CGAffineTransform CGAffineTransformMakeYShear(CGFloat proportion);
CGAffineTransform CGAffineTransformYShear(CGAffineTransform src, CGFloat proportion);


#import "CGAffineTransformShear.h"
CGAffineTransform CGAffineTransformMakeXShear(CGFloat proportion)
return CGAffineTransformMake(1.0, 0.0, proportion, 1.0, 0.0, 0.0);
CGAffineTransform CGAffineTransformXShear(CGAffineTransform src, CGFloat proportion)
return CGAffineTransformConcat(src, CGAffineTransformMakeXShear(proportion));
CGAffineTransform CGAffineTransformMakeYShear(CGFloat proportion)
return CGAffineTransformMake(1.0, proportion, 0.0, 1.0, 0.0, 0.0);

CGAffineTransform CGAffineTransformYShear(CGAffineTransform src, CGFloat proportion)
return CGAffineTransformConcat(src, CGAffineTransformMakeYShear(proportion));

Now, we can shear a view, even one we create in Interface Builder:

The red and the green parallelograms in the screenshot to the left are just UIViews with a shear transform applied, using the functions above.

Have fun!

Oh, and if you want it - here's the revised Xcode project from the last article using shear.

Demystifying CGAffineTransform

One of the most common questions I get about iPhone programming is about how to rotate or scale or make various other changes to a view. I'm not talking about hardcore Core Animation kind of stuff, just simple, "How do I place a label at 45°" kind of questions. The expectation is that there should be a property called "angle" or "scale" that can be set, or that you should be able to hold down the option key in Interface Builder to rotate it there.

With Leopard, Apple gave us Core Animation,and it is very cool, but in order to achieve all that coolness, they had to add some concepts that make it not always intuitive. (BTW: If you do want to know more about Core Animation, I've been reading Bill Dudney's Core Animation for Mac OS X and the iPhone and it's very good).

Any change to a view's position, scale, or rotation can now be stored in a property of the view called transform. It's a CGAffineTransform struct, and it's a bit cryptic if you've never worked with transformation matrices before.

A transformation matrix nothing more than a two-dimensional array of numbers. Okay, perhaps I shouldn't say "just", as transformation matrices are quite powerful. They can store complex changes to the position and shape of an object, including rotating, scaling, moving, and skewing (or shearing) the view as it's drawn. This adds a little bit of programmer complexity if you want to do anything more than the absolute basics, but it opens up a world of possibilities.

The CGAffineTransform Data Structure

So, what does this data structure look like? This:

struct CGAffineTransform {
CGFloat a;
CGFloat b;
CGFloat c;
CGFloat d;
CGFloat tx;
CGFloat ty;

yeah, it doesn't look like a matrix, does it? It is; it'sit is a 3x3 matrix, it's just that certain values in the matrix are constant, they can't change, so they're not represented by a variable. Here's what the matrix would look like drawn out in human-friendly form:

| a b 0 |
| c d 0 |
| tx ty 1 |

These 9 numbers are used to store the rotation, scale, and position of an object using something called Matrix Multiplication.
Note: By the way, this exact same process is used to transform shapes in three-dimensional graphics. The matrices used for 3D are 4X4 instead of 3x3 to capture the additional z dimension.

So, if a view has a transform, how does Core Graphics figure out how and where to draw it?

Basically, it figures out where it would draw each point (x,y) without the transformation, and then does the following math to figure out the new, transformed point:
new x position = old x position * a + old y position * c + tx
new y position = old x position*b + old y position * d + ty

And that works? Yep, it does, amazingly enough. If you're interested in the math behind it all, there are many good sources. Just google "Matrix Transformation" to find some. If you're going to be doing complex transformations, it's a good idea to have a basic understanding of the underlying maths, but for basic usage, you can get away without it.

The Basic Transformations

The reason you can get away without understanding the intricacies of the math is because Apple has provided us with a number of functions to retrieve standard matrices and to standard transformations. In order to use any of these transformations, you will need to include the CoreGraphics framework in your project, and include the CoreGraphics header file:
#import <CoreGraphics/CoreGraphics.h>

The Identity Transformation

All views (and layers, but we're not talking about layers today) start out with their transform property set to the Identity Matrix. This matrix represents the object without any changes. It hasn't been rotated, scaled, sheared, or translated (moved). For a view that has the identity matrix for the transform property will be drawn based solely on the size and origin in the bounds property.

Note: Views have both a frame (coordinates in superview's coordinate system) and bounds (coordinates in own coordinate system) property, but if you transform a view, you should not use or rely on the frame property anymore. If you are using transformations, work with the bounds property only, not the frame property, as transformations are applied to the bounds, but aren't necessarily reflected accurately in frame

Any time you want to reset a view or layer to its original, untransformed state, you simply set its transform to the Identity Transformation using the constant value CGAffineTransformIdentity like so:
theView.transform = CGAffineTransformIdentity;

The Translate Transformation

Translation is just a fancy way of saying "moving". You can, of course, accomplish a move by changing the origin value of the view's frame property (which moves the view in relation to its superview), but since we can't use the frame property along with other transformations, the translate transformation is an important one. If you want to translate a view, you use a Core Graphics function called CGAffineTransformTranslate(). This method takes three paramters. The first is an existing CGAffineTransform value that the translation will be applied to. To translate a view from its current position, you would pass the view's transform property here. To translate the view from its original position, you would pass in CGAffineTransformIdentity. Here is an example that would move the view five points to the right and ten points down.
theView.transform = CGAffineTransformTranslate(theView.transform, 5.0, 10.0);

Note: "points" or "units" generally mean pixels, but as we're moving to resolution independence and starting to support the third dimension, it's no longer correct to say it's always and forever true that one point is one pixel. But, it usually is

Matrix multiplication is cumulative, so if you translate by five pixels, then translate again by five pixels in the same direction, you get a translation of ten pixels, assuming that there were no other transformations in between the two calls.

The Rotation Transformation

The next most common translation, and the first one we're discussing that can't be done without transformations, is rotation, which is handled by the function called CGAffineTransormRotate(). This function takes two parameters, the first being the existing transformation matrix, and the second being the angle of rotation expressed in radians.

Radians? Who the heck thinks in radians? There's a convenience conversion macro in Core Graphics for Mac OS X called degreesToRadian(), but right now, it's inexplicably absent from Core Graphics for iPhone. It's an easy enough conversion, though - just add this line of code to your header file:
#define degreesToRadians(x) (M_PI * x / 180.0)

then you can rotate a view like this:
theView.transform = CGAffineTransformRotate(theView.transform, degreesToRadians(45));

The Scale Transformation

The final of the basic transformation is the scale transformation, which allows you to resize your view without touching its bounds property. To scale a view to double its original size, we use CGAffineTransformScale(), like so:
theView.transform = CGAffineTransformScale(theView.transform, 2.0, 2.0);

Note: If you are transforming the Identity Matrix, you can use the "Make" version of these functions which do not take a CGAffineTransform as a parameter, and just assume the Identity Matrix. So, for example, calling:
theView.transform = CGAffineTransformTranslate(CGAffineTransformIdentity, 2.0, 2.0);

You could call
theView.transform = CGAffineTransformMakeTranslation(2.0, 2.0);

Those two lines of code are functionally identical.

Some Things to Be Aware Of

Here are a few things that you should make note of as you start working with transformations.

The Center of the World

When you are scaling or rotating, the object will get scaled or rotated from the center of the object. In Core Animation, you can set an Anchor Point that will change that behavior, but if you are not using Core Animation and don't want to deal with layers, then in order to scale or rotate from, for example, you would have to also have to manually do translation transformations to reposition the view after the scale or rotation. Which brings another thing to mind:

Order Matters

When you apply success transformations, the order matter. Rotating and then translating will give you a different result then translating and then rotating. This can bite you if you're not careful.

Stepping Back

As I said earlier, you can always get back to the starting point by setting the view's transform to the Identity Matrix. But, what if you just want to back out one transformation. Say, you rotated, then scaled, then translated, and you just want to "untranslate" it. This can be useful if, for example, you want to do complex animations, such as having a view move one way, and then return to its original position. There is another transformation to look at called the Inverse transformation. The inverse of a transformation is the translation that will negate that translation when applied after it. You can get the inverse transformation for any CGAffineTransform by using the function CGAffineTransformInvert(), like so:
CGAffineTransform inverse = CGAffineTransformInvert(CGAffineTransformMakeTranslation(5.0, 5.0));

The value of inverse in the code above is the same as creating a translation of (-5.0, -5.0), but you don't have to know what the transformation is to get the inverse using this method.


Okay, we've only scratched the surface of what is a very complex part of the iPhone, but I hope this helps make the concept of "transforms" and "transformations" more approachable and will help some people make more sense of the documentation. As always, if you have questions, feel free to ping me via e-mail or IM, or send a tweet my way. I use the same username every where, which is jeff underscore lamarche, except for gmail, where I'm jeff dot lamarche.

Here's a sample Xcode project that shows how to use some transformations on views created in Interface Builder.

I'm Flattered, I Think...

I received my first Press Release today. I think I should be flattered that somebody thought enough of my little patch of space on the intertubes to feel like sending me a Press Release would be of any value.

I'm not sure what to do with it, to be honest. I have no interest in being a shill, especially not for free, but not even for pay. If I wanted to be a sell-out, I'd still be an attorney. Press Releases (and this one isn't an exception) generally have a low signal-to-noise ratio and are filled with obnoxious puffery designed to bathe one particular company's products or services in a glowing, heavenly light. Reading most Press Releases just makes me cringe. I hate marketing-speak, and I especially hate when there's so much of it that I can't even discern the point they're trying to make.

On the other hand, if something would be of value to the few people who come here, I would like to pass the information on. I just can't bring myself to post formulaic press releases and am honestly not motivated enough to figure out what the hell the real message is, if there even is one.

For any Marketing-type folks who happen across this: If you want me to share information for your, I'll be happy to spread the word if it's relevant to the topics I cover. Send me the meat of the message in plain English, forget about the hyperbole and puffery, and get to the point. If it's something related to the iPhone SDK, I'll almost certainly blog it, but don't treat me as an extension of your PR department, especially if you're not going to have the decency to offer me a bribe.

(I'm just kidding about the bribe, of course.)


Hey, look! Another SOAP posting.

A reader with the Google name of EasyShout very kindly pointed me to a project on Google Code called WSDL2ObjC, and I'm quite appreciative. Although I'm not a huge fan of code generation in general, I welcome any solid, usable solution to the iPhone's lack of SOAP support, and this looks to be pretty good. Besides, code generation has a long history in the world of SOAP; we wouldn't want to be the only language without a good tool for generating stubs from WSDLs, would we?

So, if you're still looking for a good SOAP solution, check this one out. If and when I can find some free time, I'm going to try it out myself, and if I do, I'll post my findings.

Saturday, October 25, 2008

Table View Multi-Row Edit Mode

If you've played around at all with UITableView's "Edit Mode", you've probably been disappointed that it doesn't support the ability to select and then delete multiple rows in the table, the way that you can do in Apple's Mail application. It was one of the most welcome improvements made in the 2.0 iPhone OS, and I was a bit bummed when I discovered that the ability to do that was not being added to UITableView with the 2.0 release.

Personally, I'd like to see the functionality in more table-based iPhone apps, so I threw together a little sample iPhone project that shows how to do it. You can find the project Right Here.

I'm not going to walk through the entire projects, as most of it is standard application-building, but I wanted to point out the general approach I used. I do not know if this is exactly how Mail does it, and I'm certainly not sure this is the best way to do it, but it does work. The only aspect of the Mail implementation I didn't get is changing the background color of the selected rows in edit mode. I tried it, but was getting some weird behavior where the last-selected row was turning back to white, but when another row was added to the selection, then it would return to the correct color. At some point, I'll dive in and try and figure out what was wrong with that code, but for the time being, this should work pretty well for you and at least give you an idea of how the process can work.

In my controller class, I defined a few constants and macros:

#define kCellImageViewTag 1000
#define kCellLabelTag 1001

#define kLabelIndentedRect CGRectMake(40.0, 12.0, 275.0, 20.0)
#define kLabelRect CGRectMake(15.0, 12.0, 275.0, 20.0)

The first two will be used later to retrieve the correct subviews of the table view cell. The bottom two define the possible positions of the row's text. If we're in edit mode, the text is going to be moved over a little bit (which will be animated). By defining the two rects here, we can shift the text over easily by simply assigning the new value to the label's frame property.

In my controller, I have two mutable arrays. One will hold the display values, the other will be used to hold which rows are selected when we're in edit mode. I also define a BOOL that will identify when we're in edit mode. I don't call it edit mode because I don't want to risk a name conflict or confusion with Apple's code.

NSMutableArray *countries;
NSMutableArray *selectedArray;
BOOL inPseudoEditMode;

I also have two UIImage pointers that contain the checked and unchecked image. This is a little klugey - the unchecked is just a circle, so I probably should have just used CoreGraphics to draw the circle, but this was easier.

UIImage *selectedImage;
UIImage *unselectedImage;

I created a method that will create the selectedArray, populating it with NSNumber objects that hold a NO value for every row. This lets me easily reset the selection after a delete.

- (void)populateSelectedArray
NSMutableArray *array = [[NSMutableArray alloc] initWithCapacity:[countries count]];
for (int i=0; i < [countries count]; i++)
[array addObject:[NSNumber numberWithBool:NO]];
self.selectedArray = array;
[array release];

This method gets called in viewDidLoad, and also every time we delete rows. The viewDidLoad method also loads an array with strings pulled from a text file and loads the two UIImages.

There's an IBAction method to toggle edit mode. This gets called when the user presses the "Delete" button in the Nav Bar. It changes the value of inPsuedoEditMode and also hides or unhides the toolbar at the bottom, which has the "Delete" button that causes selected rows to get deleted.

self.inPseudoEditMode = !inPseudoEditMode;
toolbar.hidden = !inPseudoEditMode;

[self.tableView reloadData];

Most of the work here is in the tableView:cellForRowAtIndexPath: method. Here is where we have to look at whether we're in edit mode, and if we are in edit mode, look at which rows are selected.

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
static NSString *EditCellIdentifier = @" editcell";

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:EditCellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:EditCellIdentifier] autorelease];

UILabel *label = [[UILabel alloc] initWithFrame:kLabelRect];
label.tag = kCellLabelTag;
[cell.contentView addSubview:label];
[label release];

UIImageView *imageView = [[UIImageView alloc] initWithImage:unselectedImage];
imageView.frame = CGRectMake(5.0, 10.0, 23.0, 23.0);
[cell.contentView addSubview:imageView];
imageView.hidden = !inPseudoEditMode;
imageView.tag = kCellImageViewTag;
[imageView release];


[UIView beginAnimations:@"cell shift" context:nil];

UILabel *label = (UILabel *)[cell.contentView viewWithTag:kCellLabelTag];
label.text = [countries objectAtIndex:[indexPath row]];
label.frame = (inPseudoEditMode) ? kLabelIndentedRect : kLabelRect;

UIImageView *imageView = (UIImageView *)[cell.contentView viewWithTag:kCellImageViewTag];
NSNumber *selected = [selectedArray objectAtIndex:[indexPath row]];
imageView.image = ([selected boolValue]) ? selectedImage : unselectedImage;
imageView.hidden = !inPseudoEditMode;
[UIView commitAnimations];

return cell;

Notice a few things

  • we manually create subviews to the table view cell's content view, and we assign them tags. The tags allow us to retrieve the correct subview when we get dequeued cell instead of creating a new one.

  • We call beginAnimations:forContext: and commitAnimations: around our changes so that the changes get animated for us. That's all we have to do to make turning edit mode on and off animated

When a row is touched, and we are in edit mode, we have to set the corresponding row in the selection array to YES if it's currently NO and vice versa.

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
[self.tableView deselectRowAtIndexPath:indexPath animated:YES];
if (inPseudoEditMode)
BOOL selected = [[selectedArray objectAtIndex:[indexPath row]] boolValue];
[selectedArray replaceObjectAtIndex:[indexPath row] withObject:[NSNumber numberWithBool:!selected]];
[self.tableView reloadData];

There's one more method that's key to this process, which is another action method that gets called when the Delete button in the toolbar gets pressed. Because this toolbar is only shown when we're in edit mode, we don't have to check that, we just do the delete. Because you can't delete objects from a collection while enumerating over them, this method is a little more complex than you might expect.

NSMutableArray *rowsToBeDeleted = [[NSMutableArray alloc] init];
NSMutableArray *indexPaths = [[NSMutableArray alloc] init];
int index = 0;
for (NSNumber *rowSelected in selectedArray)
if ([rowSelected boolValue])

[rowsToBeDeleted addObject:[countries objectAtIndex:index]];
NSUInteger pathSource[2] = {0, index};
NSIndexPath *path = [NSIndexPath indexPathWithIndexes:pathSource length:2];
[indexPaths addObject:path];

for (id value in rowsToBeDeleted)
[countries removeObject:value];

[self.tableView deleteRowsAtIndexPaths:indexPaths withRowAnimation:UITableViewRowAnimationFade];

[indexPaths release];
[rowsToBeDeleted release];
inPseudoEditMode = NO;
[self populateSelectedArray];
[self.tableView reloadData];

Anyway, I hope this is helpful to some people. If you have any questions, put them in the comments, or drop me an e-mail.

Friday, October 24, 2008

Captain Obvious Strikes Again

In the Xcode editor pane (the part of the window where your source code is displayed), you can option-double-click any term to search for it in the Documentation Browser. You can also command-double-click any term to open up its definition in the public header files.

That is all.

It's Beta, but it Shows they are listening...

New, official Dev Discussion Forums hosted by Apple.

Seems pretty cool so far, volume is low but increasing rapidly. C'mon over and join the discussions. Haven't seen much of a presence by "official" Apple folks yet, but still a good place to take a swim.

Combine this with the NDA drop and it tells me that people at Apple are listening to what Developers are saying. They might not always respond as fast as we'd like, but they do respond. Yay, Apple.

SOAP Web Services Redux

I should have posted a follow-up long before now, so my apologies. Some of my earliest postings here were on accessing Web Services from the iPhone. At the time I wrote that posting, I had not yet been accepted into the iPhone developer program, and wasn't aware that CoreServices.framework existed in the simulator, but not on the device.

I got accepted into the program and discovered the problem just before WWDC, and spent a good part of that conference trying to corner somebody from Apple about it. I was not able to get anyone who was even aware of the discrepancy, let alone somebody who could tell me whether the framework was intentionally left off of the device or if it would ever be brought over. The best I got was a very non-committal, off-the-record statement that WebServicesCore probably "wasn't long for the world". It hasn't been updated for a few years, and probably won't be. REST is the way of the future, why bother with SOAP, seems to be the feeling.

Of course, there is a huge installed base of SOAP web services which, I would argue, is a good enough reason to update and expand WebServicesCore. More importantly, many of the people coming to the iPhone are coming from .NET, which has extremely robust support for SOAP web services. I would argue that not having a good SOAP client in Cocoa Touch or Foundation makes our platform look bad.

Anyway, if you do need to access SOAP web services from the iPhone, you're stuck rolling your own or looking for a third-party SOAP library. There is an excellent thread over at iPhoneDevSDK. Right now, that's the best source of information I have to offer anybody about SOAP web services.

Now, if you're interested in RESTful web services, Apple has an article on that. In fact, they have an article that I co-wrote.

Thursday, October 23, 2008

Crimson FX Open Sourced

This project contains the source code for a Mac OS X digital video effects editor. Primarily designed to allow key-framed animation of laser and lightsaber effects, I had started to expand it into a more general-purpose effects editor.

The interface is horrible, could use quite a bit of help. I stopped working on this when Quicktime 7 came out and broke the compression code I was using. I lost momentum then, and never picked it back up. It still compiles, and it should work if the compression code is bypassed.

This was done pre-Core Image, so some of the code that takes advantage of hardware acceleration is probably a bit outdated. I also rolled my own convolution filter for applying blurs and other effects, but that code should really be converted to using Core Image.

I don't have any plans to start active development on this one again, but if there's anyone who wants to take it over, I'm happy to give you administrator status on the project.

Another Open Source Project

This project's a little more frivolous, probably won't be too much interest in it, but the code works, and somebody out there might have need of code that creates red/blue stereograms from two source images. This Mac OS X program makes those 3D images that you need the red/blue glasses to view.

It might be kind of neat to make a dual-iPhone version of this, where you put two iPhones next to each other, takes one picture from each, and then stitches them into a single stereo image aka an anaglyph. Don't think that can be fully automated with the official SDK, though.

Scroll Views

I've been realizing over the last couple of days that we missed covering something in the book that we should have: UIScrollView. Now that I've spent a few days fighting them, I must admit that I'm glad I missed it. These things are complex and not as well documented as they should be. I've got my app working with hit testing inside of a scroll view, and without jaggies, but my performance isn't good. Here's the thing:

UIScrollView ALWAYS starts at a zoom of 1.0. You can't change this. If you do, it will just cause it to act funny the first time the user touches the screen (please, if I'm wrong on this, correct me). But, if you zoom in on a view, it gets all pixelated and blocky unless you change your content view's (and/or subview's) backing layer to a CATiledLayer. Doing that kills performance on my first generation iPhone. I haven't tested it yet on my second generation iPod Touch, but I suspect it will only be a little bit better.

But, here's the thing. If I change the size so that I start zoomed in... so that the content view is the size of the zoomed view and don't use CATiledLayer, it works beautifully, scrolls fast, no skips, etc. But, I don't want the user to have to start zoomed way in. The program won't be intuitive if I do that.

A related problem is that I can't get the double-tap zoom and unzoom working. In an old edition of the iPhone Programming guide, there was sample code that supposedly showed how to do that, but I've tried it, and many, many variants of it, and never have gotten it to work right. There might be a reason why that code sample is no longer in the programming guide.

Anybody out there gotten this working?

Cocoa Barcodes

The Cocoa Barcodes project (formerly Barcode Generator) is now available at:

Cocoa Barcodes is a set of classes (and a test application) for generating two-dimensional barcodes. It supports many of the more common one-dimensional linear barcodes in use today, allows you to export a barcode as a TIFF, EPS, or PDF image, to copy the barcode image to the pasteboard, or to drag it to any other application that accepts standard OS X PDF data from the pasteboard, including TextEdit?. You can also print barcodes directly to any supported printer. Please note that you may not be able to create readable barcodes at all bar widths allowed by a specification. For example, Code 3 of 9 allows a bar width of as small as 7.5 mils, but I haven't had much luck going smaller than 13 mils on ink jet printers.

You have a fair amount of control over the final appearance of the barcode, including the bar width (in 1/10 mil increments), bar height, font size, and captioning. The following barcode types are supported:

  • Code 3 of 9

  • Extended Code 3 of 9

  • Code 128

  • Interleaved 2 of 5

  • Industrial 2 of 5

  • Codabar

  • PostNet

  • Modified Plessey

  • Modified Plessey (hexadecimal)

  • UPC-A

  • UPC-E

  • EAN-13

  • EAN-8

  • Royal Mail Barcode (also known as RM4SCC or CBC)

  • Planet Barcode

  • Japan Post Barcode

Cocoa Barcodes is based on Barcode Generator, an open source Mac program which began its life as a test scaffold for a set of Cocoa classes I was writing. I did not initially intend to release it as a standalone program, but by the time I was done testing the code, it had the lion's share of the features available on other OS X barcode programs at the time so I decided to release it.

I intend to add iPhone support at some point, but currently, drawing the barcodes is accomplished using categories on NSView and NSImage, neither of which are available on the iPhone.

Old is New

Sitting on my hard drive, I've got several Cocoa projects I've written over the years. For most of these, the source code used to be available on the web, but I stopped maintaining the site that hosted them. I'm going to go through those and see which ones may still have practical applications or have code that could be useful for the iPhone and start checking them into Google Code. I periodically raid those projects for code for iPhone projects, so I'm pretty sure there are diamonds left in the mine, so to speak. Well, cubic zirconia, at least.

First up is a set of Cocoa classes for generating bar codes. The code supports almost all two-dimensional barcode symbologies, and is fairly well-tested and stable, having been used in a couple of commercial and in-house applications. I'm not sure if there'd be much value in it, but it shouldn't take much to get it running on the iPhone if anyone needs it. I wonder if you can scan the iPhone's screen with a barcode reader? There might be some cool applications if you can... Does anyone have a barcode scanner and iPhone handy who can test that??

Currently, the code uses categories on NSView and NSImage to do the drawing. It shouldn't take too much effort to make a UIView and UIImage category to do the same thing. The NSBezierPath calls will have to be changed to use CG calls, but I can't imagine it being more than an hour's work (famous last words).

I'll post when I get the Barcode Generator source code uploaded, hopefully will be later today.

Wednesday, October 22, 2008

You Shouldn't, but You Will...

Class-Dump is an essential tool in the Cocoa Programmer's arsenal. It will read a compiled Objective-C binary and print out the header files for all classes used in that file. Depending on the settings used to compile, it may not have the correct variable names, but it will have the correct method signatures, even those that are not declared in the public headers.

Now, for the iPhone, we can't use Class-Dump, because it doesn't recognize binaries compiled for the ARM6 processor. Additionally, we shouldn't use it, because it means we're poking around in private stuff that could get our Application banned from the App Store.

But, for the curious, I thought I'd point out that you can actually use Class-Dump on iPhone frameworks; you just have to run it on the framework that's in the SDK for the simulator rather than the device. The iPhone simulator is NOT an emulator.. it's not running ARM6 byte codes, it's running X86 byte codes (except for those naughty people who installed the SDK on a PPC Mac).

So, want to see the headers from the UIKit in all their glory?

cd /Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator2.1.sdk/System/Library/Frameworks/UIKit.framework
class-dump UIKit > ~/Desktop/UIKit.txt

But, shhhh.... You didn't learn it from me.

Getting the contents of a UIView as a UIImage

In Cocoa, it's really easy to take the contents of an NSView and convert them to an NSImage using dataWithPDFInsideRect:. I needed to do the same task on the iPhone, so immediately looked for a comparable method. I didn't find one.

Thankfully, Google came to the rescue. Josh Goebel shows how to do it right here.

Note: To use this in your project, you'll have to link to the QuartzCore framework and also #import <QuartzCore/QuartzCore.h>

Shuffling Arrays

Ever want to randomize an array of items? It's a task that, for some reason, I've had to do a lot in recent programs. So, I wrote a handy category on NSArray to handle the task.



@interface NSArray(Shuffle)
-(NSArray *)shuffledArray;


#import "NSArray-Shuffle.h"

@implementation NSArray(Shuffle)
-(NSArray *)shuffledArray

NSMutableArray *array = [NSMutableArray arrayWithCapacity:[self count]];

NSMutableArray *copy = [self mutableCopy];
while ([copy count] > 0)
int index = arc4random() % [copy count];
id objectToMove = [copy objectAtIndex:index];
[array addObject:objectToMove];
[copy removeObjectAtIndex:index];

[copy release];
return array;

Encodings Can Byte You

It is 2008, right? I mean, in this day and age, it's not totally unreasonable to expect that NSString to default to using an NSUTF8StringEncoding as the default encoding when loading a file if it can't determine the encoding, right? I mean, since an ASCII file will load correctly using UTF-8, but not vice versa, UTF-8 seems like the best assumption or, at least, a better assumption than ASCII.

Well, it might be a "reasonable" assumption, but it's an incorrect one. NSString's initWithContentsOfFile: apparently assumes an encoding of NSASCIIStringEncoding when it can't determine the real encoding.

This, I'm embarrassed to say, bit me today. I had the following code that I was using to load a UTF-8 file with non-ASCII characters:

NSString *sourcePath = [[NSBundle mainBundle] pathForResource:@"act texts" ofType:@"txt"];
NSString *sourceData = [[NSString alloc] initWithContentsOfFile:sourcePath];

But the resulting strings didn't contain the correct non-ASCII characters that were in the file; every time there was supposed to be a diacritical or other non-ASCII character, the string contained two high-order (>128) ASCII characters. That's an indication that you've got UTF-8 data being loaded as ASCII (UTF-16 looks even weirder when it misses the encoding, making it easier to catch).

The solution is simple enough. Just explicitly tell it the encoding to use by calling initWithContentsOfFile:encoding:error: instead :

NSString *sourcePath = [[NSBundle mainBundle] pathForResource:@"act texts" ofType:@"txt"];
NSString *sourceData = [[NSString alloc] initWithContentsOfFile:sourcePath encoding:NSUTF8StringEncoding error:nil];

Tuesday, October 21, 2008

Idle Timer

If you're making a game, please, please, please remember to turn off the idle timer. The Force Unleashed, a big-budget game loosely modeled after the console game of the same name, is a moderately fun, very polished game, but the screen constantly dims during the game in cutscenes and other places where you're not touching the screen for a while.

C'mon, folks: it's one line of code. Use it.

[UIApplication sharedApplication].isIdleTimerDisabled = YES;

Starting in Landscape Mode without Status Bar

Here's another situation where the Simulator doesn't behave the same as the device. It's also something that's not well documented, so let's take a second to look at how to have an application start up in landscape mode without a status bar.

The first thing you have to do is open up Info.plist in your Xcode project. It will be in the Resources group. You need to add two entires. First, add an entry called UIInterfaceOrientation and assign it a value of UIInterfaceOrientationLandscapeRight. Second, ad another entry, and call it UIStatusBarHidden. When you add this row, it should change to a checkbox; make sure the box is checked.

Now, in your application delegate, find the method called applicationDidFinishLaunching:. In it, you need to add the following code, after the last line that's already there. The code you need to add should look like this:

[[UIApplication sharedApplication] setStatusBarOrientation:UIInterfaceOrientationLandscapeRight animated:NO];

UIScreen *screen = [UIScreen mainScreen];
viewController.view.bounds = CGRectMake(0, 0, screen.bounds.size.height, screen.bounds.size.width);
viewController.view.transform = CGAffineTransformConcat(viewController.view.transform, CGAffineTransformMakeRotation((M_PI * 90 / 180.0))); =;

After adding this code, your application, when run on the iPhone will rotate and resize the root view automatically just by virtue of having set the statusBarOrientation to UIInterfaceOrientationLandscapeRight. That's not the case when running it on the simulator, which is why the block of code in the conditional is necessary. With that, the code should behave exactly the same on the device and in the simulator.

To compile this code, you're also going to need to add the CoreGraphics framework. Make sure to add the framework using a reference type of "Relative to Current SDK'. The version for the device is located here:


SQLite Persistent Object Update

Last night, I fixed a bunch of bugs in the SQLite Persistent Objects code. I also wrote an iPhone application that uses it to save its data, and checked the project source code into Subversion as well. I plan to write a basic tutorial around this application, but wanted to make it available for anyone who wanted to see it in action. If you check out the project from Subversion, you should get a new folder called Sample Code. The Xcode project is in there; the links from the project back to the SQLite Persistent Objct code is project-relative, so if you put the Sample Code project anywhere else but in your sqlitepersistentobjects folder, you're going to have to relink those files.

I would appreciate it if someone could try checking it out and compiling it to make sure it works. The program uses the camera, but it can be run on the simulator,the "Take Picture" just won'tt work. If you want to run the sample code on the device, you'll have to change the bundle identifier, developer identity, and developer cert, of course.

Monday, October 20, 2008

Device vs. Simulator

The iPhone Simulator is a really cool piece of software. Although I do most of my development testing on an iPhone or iPod Touch, I really like having the option to run code when I don't have a device handy. It's a really cool piece of technology.

Sometimes, it can be downright annoying, though. Today, I hit an example of that. I'm working on a project that needs to run on both the Mac and the iPhone, and it does a fair bit of mucking around in the runtime. I've written programs using for both the Mac and the iPhone with no problems, but periodically would get e-mail from someone asking if I could make it work for the iPhone.

Well, it turns out *blush*... I must have never actually tested the code on an iPhone or iPod Touch, and only used this particular code in the simulator and on the Mac. You see, I have this line of code:

#import <objc/objc-runtime.h>

And that code works just fine and dandy for the Mac, and for the iPhone Simulator. But, guess what? obj/objc-runtime.h doesn't seem to exist in the iPhone SDK, so when you switch the SDK to the device and then compile, the build goes down in a blaze of gory (no, not glory, gory... it's ugly).

Fixing it was relatively trivial once I found the problem. The file objc/objc-runtime.h is a very simple header file. Here is what it looks like on the Mac:

#import <objc/runtime.h>
#import <objc/message.h>

That's it. And both of those files do exist for the device SDK. So, I simply replaced the one #import <objc/objc-runtime.h> statement with the two #import statements it contained, and voilá, it started working again. Mostly.

It compiled with no errors, but I got a whole bunch of warnings, all centered around the use of two methods it couldn't find: -className and +className. These methods do nothing more than return the name of the class, one is implemented as an instance method, the other as a class method. I have no idea why these two methods don't exist for the device SDK, but this was also easy enough to fix, since the class name is available through runtime calls.

I added the two methods, but wrapped the code in a pre-compiler conditional statement so it only gets used when compiling for the iPhone:

So, in the header file:

- (NSString *)className;
+ (NSString *)className;

Currently, this resides on the class where I needed it, but I'm going to move it into a category on NSObject. The implementation of these two methods is nearly as short:

- (NSString *)className
return [NSString stringWithUTF8String:class_getName([self class])];
+ (NSString *)className
return [NSString stringWithUTF8String:class_getName(self)];

And that's all for today, I'm going to bed.

Another Couple of Tips by Captain Obvious

The iPhone SDK is so large, it's easy to miss things that other people think are obvious. Because of that, I'm going to post another tip that most people probably know already, but that some people might now.

If you create a PNG file of size 320x480 and call it "Default.png" (spelled exactly that way, making sure you have the first letter capitalized), you can then add that image to your Xcode project's Resources group and it will act sort of like a splash screen for our application - it will show that image until your application is fully loaded.

Although I'm not a big fan of splash screens, it's a good idea if you've got a slow-loading application to let the user know everything is proceeding okay. If you've got a slow-loading application, and you don't know why, it may be because you have a lot of resources in your project. The iPhone seems to do some kind of check on application launch, and the more individual files you have in your application bundle, the longer it takes. The actual size of the files doesn't seem to matter, but the number of files definitely does. If you're in this situation, consider reducing the number of files in your bundle somehow. A fairly easy way to do that is to store all those files as blobs inside a single SQLite database. You can use a read-only database from your bundle without copying it to the Documents folder, but you must make sure not to write to it, because if you change anything in your application bundle, code signing for the application will stop working and the user will not be able to launch it again. You can use a separate SQLite database in your application's Documents folder for user data.


I thought everybody knew this by now, but I have encountered two people recently who have been developing for the iPhone for a while and who didn't know this, so here it is. Sorry if I'm being Captain Obvious.

If you want to simulate a two-finger gesture in the iPhone simulator, hold down the option key. You will get two dots on the screen instead of one. The two dots will default to pinching - if you bring the dot closer to the center of the screen, the other dot comes toward the center, making it easy to simulate a pinch in or pinch out.

If you want to do a different two-finger gesture, get the two dots the distance apart that you want them to be, then hold down the shift key, while still holding down the option key. That will lock the position of the two finger presses together so you can do, for example, a two-finger swipe.

Still don't know a way to do three-or-more finger gestures, or complex two-finger gestures, but the use of the shift and option key should cover about 95% of the gestures you'd need.

iPhone "Optimized" PNGs

For the most part, Apple's developer documentation for both the Mac and iPhone is excellent. They are well-written, accurate, and provide excellent code samples. There are, of course, always gaps, especially with newer areas. Sometimes these gaps are simply a matter of resource constraints; the volume of documentation the documentation teams have to maintain is staggering, and frameworks are constantly being added and updated.

At other times, Apple is tight-lipped about stuff not because of resource constraints, but rather intentionally, though it's not always clear why. Do you want to know how fast the processor in your iPhone is, or how much memory is available to your application? Both of these are obviously relevant to developing for the iPhone, but don't look to Apple for that information. The information is available (processor | memory), just not from Apple.

Here's another area where Apple is less than fully forthcoming: When it comes to the iPhone's use of PNG images, Apple tells you that Xcode "optimizes" PNGs as part of the build process and, as a result, you should always use PNG images in your iPhone projects. PNG images will usually be bigger than JPEGs, causing your application to be a little larger, but you'll be rewarded by some mysterious kind of improvement.

Since this information is not documented, what follows is something of an educated guess based on research and observations. I will gladly be corrected on any inaccuracies, so don't hesitate to ping me if you see something wrong.

So, just what is this magical, mystery "optimization"?

During the build, Xcode basically screws up your PNG image, turning it into something that's technically no longer a PNG image. Xcode doesn't change your original file, but when it copies it to the Resources folder of your application bundle, what it does is it byte-swaps the red and blue octets and also "premultiplies the alpha" (if that doesn't make sense, don't worry, we'll talk about it in a moment). The PNG specification does not support either of these changes, which is why the image is no longer technically a PNG and can't be loaded by most image editing software. Not that it really matters, since the new version only exists inside your application bundle, but it does mean that any PNG file that you include in your app bundle should not be, for example, FTPed or e-mailed from your application directly, because the file will be corrupt as far as most software is concerned.

Byte Swapping

Byte swapping is exactly what it sounds like. Uncompressed computer graphic images are most-often stored as sequences of three or four bytes or "octets" representing each pixel in the image. Each byte in the pixel represents one of the three additive primaries (red, blue, and green), plus there's often another byte called "alpha", which we'll look at in a moment. There are other ways to store images, but this is the most common technique. The most common byte-ordering used in this technique is RGB (or RGBA) which stands for Red-Green-Blue(-Alpha). This means that a single pixel is represented in memory by four bytes, the first representing the intensity of red, the second representing the intensity of green, and the third representing the intensity of blue (we'll ignore alpha for now). The PNG specification uses this byte-ordering, as do many other image formats.

However, the iPhone's video memory uses a non-standard byte-ordering of BGR or Blue-Green-Red (I don't believe there's an alpha component in the iPhone's vRAM). In order to copy from an image in memory using RGBA to the video memory using GRB is more computationally expensive than just copying from, for example, BGR to BGR, which can be done with a single, fast memory move (or "blit") operation. By doing this byte-swap in the Copy Files Build Phase, your application is (in some situations) able to ignore the alpha component when loading the file into memory so it can use the faster memory move operation to get the image into video memory (and hence onto the screen).

Premultiplied Alpha

Okay, that makes sense, but what about this "premultiplying the alpha" thing? That one sounds kind of mysterious, doesn't it? As mentioned in the previous section, the iPhone's vRAM has no alpha component, so if we're going to ignore that component, we still need to take it into account somehow. Remember that PNG Images that have been optimized for the iPhone are stored as four values, representing the Blue, Green, Red, and Alpha components (in that order). Although it's called a "component", Alpha isn't really a color component at all. It's more like a modifier that acts on the other three values, and it represents how much of whatever is beneath the color will show through. So, a color that looked like this:


Would represent the color blue, but at 50% opacity. In order for the computer to use the alpha component, it has to multiply the alpha times the other three components (and possibly by other values) before putting them into video memory. This multiplication process is more computationally expensive than just copying the value into video memory. So, Xcode also premultiplies the alpha by the three components and stores the multiplied value. As a result, the color above would look like this after the Copy Files Build Phase:


Notice that the Blue component in this new pixel is equal to the Blue component of the previous version multiplied by the alpha. The result of this premultiplication, is that the alpha component can be ignored when loading the image into memory and the image can then be blitted directly to video memory without having to do the expensive floating-point multiplications to calculate the alpha. Well, at least, sometimes. This pixel is what the pixel would look like when drawn over white.

So, what happens if there's a color beneath that needs to show through? This is where things can get a little confusing. If your application is drawing the image on top of something else, or if you're using the alpha channel in the image as a mask, then the iPhone can't use this optimization. It has to do the alpha calculations (which is why the alpha channel is left intact in the pre-multiplication process), the the byte-swapping still offers some improvement. For the most part, you don't have to worry about this - it all happens under the hood. The thing you should take away from it though, is that you can help your iPhone know when it is safe to use the optimization. The way to do that is to make sure you check the "opaque" checkbox in Interface Builder for your image views, or other views that contain images, or set the opaque property of your UIImageView to YES in code. This tells the iPhone that it's safe to do the faster blit operation and ignore the alpha channel because nothing below shows through an opaque object and there's no need to do any expensive floating point alpha calculations for that object. Of course, if you are using the alpha channel in your image, or if you are doing complex image compositions in your app at run-time, you shouldn't make the view opaque. But, if you're just displaying an image in an UIImageView, checking that opaque checkbox is a really, really good idea.

An awful lot of the time, PNG images have 1.0 for the Alpha value in every pixel. As a result, more often than not, program runs faster and use less memory because of the PNG "optimizations" done by Xcode.

What happens when you use different file types

When you use any other file type (or if you load a non-optimized PNG files), your iPhone has to do the byte-swapping and alpha premultiplication at load-time (and possibly re-do the alpha multiplication at display time). Your application basically has to do the same processing that Xcode does, but it's doing it at run-time instead of at build-time. This is going to cost you both in terms of processor cycles and memory overhead. One of the reasons why Mobile Safari is the biggest memory hog of the built-in iPhone applications is because the images it has to load in order to display web-pages are all non-optimized images, mostly JPEGs. Since JPEG is a compressed format, it has the added extra step of having to decompress the image into memory before it can do the premultiplication and byte-swapping.

Wednesday, October 15, 2008

Random Thoughts: rand() vs. arc4random()

There are several built-in randomizers on the iPhone, and most people's first thought is to use rand() after seeding it by calling


But... rand() is really not a very good PRNG. random() is a little better, but still less then ideal. Fortunately, these are not the only ones available on the iPhone. Personally, I like arc4random() because it's a decent pseudo-random algorithm and has twice the range or rand().

On the iPhone, RAND_MAX is 0x7fffffff (2147483647), while arc4random() will return a maximum value of 0x100000000 (4294967296), giving much more precision. You also don't need to seed arc4random(), as the first call to it automatically seeds it.

To get an integer value from arc4random() that goes from 0 to x-1, you would do this:

int value = arc4random() % x;

To get an integer in the range 1 to x, just add 1:

int value = (arc4random() % x) + 1;

The parenthesis aren't really necessary based on order of operation rules, but I'm anal about parens.

Finally, if you need to generate a floating point number, define this in your project:

#define ARC4RANDOM_MAX 0x100000000

Then, you can use arc4random() to get a floating point value (at double the precision of using rand()), between 0 and 100, like so:

double val = floorf(((double)arc4random() / ARC4RANDOM_MAX) * 100.0f);

Tuesday, October 14, 2008


I'm really horrible at keeping up with Twitter. I recently had an influx of new people following me (lord knows why, but it's cool!), which made me realize that I hadn't tweeted since WWDC! Anyway, if you want to follow me, my Twitter name is jeff_lamarche, and I promise to try and get better about keeping it up, though I don't promise it will be even the slightest bit interesting.

In the works: An iPhone tutorial for creating applications that use SQLitePersistentObjects, which I hope to make some enhancements to in the near future.

Another ADC Article Online

Dave and I wrote this one a while back, and it's finally percolated onto the ADC web site. Pretty happy with this article, and it feels good to have another one see the light of day, even without a byline.

Saturday, October 11, 2008

Completely Off-Topic

I'm sorry, but does anybody even know why there would be such as thing as blind land speed record? That's even worse then having braille on drive-up ATMs.

Friday, October 10, 2008

A Couple More Math Snippets for 2D Graphics

Every programmer has a collection of general purpose libraries and classes that they re-use. I've got a rather extensive collection of Objective-C snippets from over the years. I periodically blow the dust off of them and use them in iPhone applications. Here's one I dug out a few weeks ago for one of the sample projects in the book.

These three functions are helpful when doing 2D graphics, either using Quartz / Core Graphics, or Open GL (but don't forget to flip the Y-axis for the latter). The first function will return the distance between two points on a 2-dimensional plane, the second will give you the absolute angle of a line formed by two points, and the third will return the angle between two lines,

#include "CGPointUtils.h"
#include <math.h>
#import "Constants.h"

CGFloat distanceBetweenPoints (CGPoint first, CGPoint second) {
CGFloat deltaX = second.x - first.x;
CGFloat deltaY = second.y - first.y;
return sqrt(deltaX*deltaX + deltaY*deltaY );
CGFloat angleBetweenPoints(CGPoint first, CGPoint second) {
CGFloat height = second.y - first.y;
CGFloat width = first.x - second.x;
CGFloat rads = atan(height/width);
return radiansToDegrees(rads);
//degs = degrees(atan((top - bottom)/(right - left)))
CGFloat angleBetweenLines(CGPoint line1Start, CGPoint line1End, CGPoint line2Start, CGPoint line2End) {

CGFloat a = line1End.x - line1Start.x;
CGFloat b = line1End.y - line1Start.y;
CGFloat c = line2End.x - line2Start.x;
CGFloat d = line2End.y - line2Start.y;

CGFloat rads = acos(((a*c) + (b*d)) / ((sqrt(a*a + b*b)) * (sqrt(c*c + d*d))));

return radiansToDegrees(rads);

Thursday, October 9, 2008

Circles, Ellipses, and Regular Polygons in OpenGL ES

The iPhone's use of OpenGL ES means that a lot of games and other programs can be ported relatively quickly. Unfortunately, the iPhone uses a relatively old version of OpenGL ES (1.1), and by the very nature of an embedded graphic engine, a lot of the niceties of the expansive OpenGL have been removed, including functions to draw a lot of standard primitive shapes.

Lines and squares are pretty easy, of course, but what about more complex shapes? Well, you're on your own for those, so unless you're comfortable with doing a little math, you're going to have problems with OpenGL ES. Here's one example - how do you draw an ellipse or circle in OpenGL? I'm not talking about a sphere (we'll look at that in a later post, maybe), but a two-dimensional circle? Or a triangle?

These two functions draw (respectively) an ellipse and a circle (which is just an ellipse with equal height and width) at a given location, either filled, or outlined. But, they actually do more then that. You can specify how precise you want the ellipse to be using the segments argument. If you specify, three, for example, it will draw a three-sided polygon (aka a triangle). If you specify 360, you'll get a 360-sided regular polygon, which is going to look like a circle on all but the biggest displays. For most purposes on the iPhone, a value above 12 will look like a circle. A value less than 3 won't work, but the error checking is your responsibility. :)

void GLDrawEllipse (int segments, CGFloat width, CGFloat height, CGPoint center, bool filled)
glTranslatef(center.x, center.y, 0.0);
GLfloat vertices[segments*2];
int count=0;
for (GLfloat i = 0; i < 360.0f; i+=(360.0f/segments))
vertices[count++] = (cos(degreesToRadian(i))*width);
vertices[count++] = (sin(degreesToRadian(i))*height);
glVertexPointer (2, GL_FLOAT , 0, vertices);
glDrawArrays ((filled) ? GL_TRIANGLE_FAN : GL_LINE_LOOP, 0, segments);
void GLDrawCircle (int circleSegments, CGFloat circleSize, CGPoint center, bool filled)
GLDrawEllipse(circleSegments, circleSize, circleSize, center, filled);

Wednesday, October 8, 2008

Radar URLs & Bug Reporting

Okay, most iPhone developers have likely discovered the Apple Bug Reporter and have likely used it on more than one occasion. If you're one of the few who haven't, though, there's the link right back there. Bookmark it, and use it. Use it for bugs. Use it for enhancements. It is the one and only official mechanism for letting Apple know about both bugs and things we don't like. Posting to forums or mailing lists - even those run by Apple - does not get your complaint in front of anybody with the ability to fix or change it.

If you do use the bug reporter, though, make sure you're thorough and follow their format. Give them detailed replication instructions. And, be formal and polite. Remember: a real person will be reading what you write, and that person may very well be the programmer who wrote the code that you don't like or think has a bug.

Here's a little thing that confuses a lot of newcomers to the Apple development world - those darn Radar URLs, the ones that look like this : rdar://problem/12345. They never work, do they? The reason is that those URLs aren't meant for you, they're meant for the internal Apple engineers with special software installed to let them access the Radar bug tracking system. There's not even a way (that I know of) to map those URLs to RadarWeb, the web-based bug-reporting tool that we all have to use, and even if you could, RadarWeb is not going to let you get to reports you didn't create or are otherwise linked to

So, next time you see one of those rdar:// urls, just remember, it's not for you and don't bother trying to click it, okay?

Wolf Rentzsh has a little more information on Radar URLs, including the format and why they're used outside of Apple.

Tuesday, October 7, 2008

A Little Color in your Life

Here are three categories I wrote on UIColor for some of my projects. I don't know how useful they'll be for you, but somebody out there might find them useful, so I thought I'd share.

The first one, UIColor(OpenGL), allows you to set the color in OpenGL using a UIColor object from the UIKit. This won't work with UIColor objects that use color spaces other than RGBA and Grayscale, but it works just fine for those. All of the UIColor class methods like +whiteColor and +blueColor return colors with one of those two color spaces, so the vast majority of the time, this will work just fine.


#import <UIKit/UIKit.h>
#import <OpenGLES/EAGL.h>
#import <OpenGLES/ES1/gl.h>
#import <OpenGLES/ES1/glext.h>
#import <OpenGLES/EAGLDrawable.h>

@interface UIColor(OpenGL)
- (void)setOpenGLColor;


#import "UIColor-OpenGL.h"

@implementation UIColor(OpenGL)
- (void)setOpenGLColor
CGColorRef color = self.CGColor;
int numComponents = CGColorGetNumberOfComponents(color);

if (numComponents == 2)
const CGFloat *components = CGColorGetComponents(color);
CGFloat all = components[0];
CGFloat alpha = components[1];

glColor4f(all,all, all, alpha);
const CGFloat *components = CGColorGetComponents(color);
CGFloat red = components[0];
CGFloat green = components[1];
CGFloat blue = components[2];
CGFloat alpha = components[3];
glColor4f(red,green, blue, alpha);


This second one will generate a random color. This version always returns a color with an alpha value of 1.0f, however you could easily modify this to make that random as well.


#import <UIKit/UIKit.h>

@interface UIColor(Random)
+(UIColor *)randomColor;


#import "UIColor-Random.h"

@implementation UIColor(Random)
+(UIColor *)randomColor
CGFloat red = (CGFloat)random()/(CGFloat)RAND_MAX;
CGFloat blue = (CGFloat)random()/(CGFloat)RAND_MAX;
CGFloat green = (CGFloat)random()/(CGFloat)RAND_MAX;
return [UIColor colorWithRed:red green:green blue:blue alpha:1.0];

This last one is very much a work in progress. I've been adding additional class factory methods to UIColor with additional colors. I find the stock set of a dozen or so colors to be kind of limiting. When I'm done, I hope to have over a hundred additional shades, but as of right now, I've only added a fraction of that, though more are sure to be coming out of a project I'm working on right now.


#import <UIKit/UIKit.h>

@interface UIColor(MoreColors)
+ (id)indigoColor;
+ (id)tealColor;
+ (id)violetColor;
+ (id)electricVioletColor;
+ (id)vividVioletColor;
+ (id)darkVioletColor;
+ (id)amberColor;
+ (id)darkAmberColor;
+ (id)lemonColor;
+ (id)roseColor;
+ (id)rubyColor;
+ (id)fireEndingRed;


#import "UIColor-MoreColors.h"

#define vendColor(r, g, b) static UIColor *ret; if (ret == nil) ret = [[UIColor colorWithRed:r green:g blue:b alpha:1.0] retain]; return ret

@implementation UIColor(MoreColors)
#pragma mark Blues
#pragma mark -
+ (id)indigoColor
vendColor(.294f, 0.0f, .509f);
+ (id)tealColor
vendColor(0.0f, 0.5f, 0.5f);
#pragma mark -
#pragma mark Purples
#pragma mark -
+ (id)violetColor
vendColor (.498f, 0.0f, 1.0f);
+ (id)electricVioletColor
vendColor(.506f, 0.0f, 1.0f);
+ (id)vividVioletColor
vendColor(.506f, 0.0f, 1.0f);
+ (id)darkVioletColor
vendColor(.58f, 0.0f, .827f);
#pragma mark -
#pragma mark Yellows
#pragma mark -
+ (id)amberColor
vendColor(1.0f, .75f, 0.0f);
+ (id)darkAmberColor
vendColor(1.0f, .494f, 0.0f);
+ (id)lemonColor
vendColor(1.0f, .914f, .0627f);
#pragma mark -
#pragma mark Reds
#pragma mark -
+ (id)roseColor
vendColor(1.0f, 0.0f, 0.5f);
+ (id)rubyColor
vendColor(0.8784f, .06667f, .3725f);
+ (id)fireEngineRed
vendColor(0.8078f, 0.0863f, 0.1255f);

That's all for today. If you have additional methods you'd like to contribute to any of these categories, by all means, send them to me at jeff-underscore-lamarche-ampersand-mac-dot-com, and I'll add them and re-publish them. Sorry for the obfuscation, but I get plenty of junk mail as it is.

Sunday, October 5, 2008

I Really Like the Layout

When we first switched publishers to Apress for the iPhone book, I was honestly a little concerned. Apress didn't have a presence in the Mac / iPhone world other than one user-oriented iPhone book, and their existing styles really didn't work, in a lot of ways, with the Mac conventions for things like menus and key shortcuts. Everything about their styles and layout seemed geared to Windows and Linux alpha geeks, and I was concerned that they just wouldn't grok that there are differences between what we needed, writing a beginner level-book for an audience of Mac users, and the needs of their existing authors.

I've now seen about half of the book in its final form and, frankly, I'm really impressed. The Apress folks did an awesome job with modifying their layout for us to accommodate the Mac and iPhone stuff we had that didn't fit in their existing styles. I think the book looks great and I couldn't be happier with the job the production folks at Apress have done accommodating the sometimes picky demands Dave and I have laid on them.

This same layout will be used for several other Mac books that Apress is planning to publish, including Lean C on the Macintosh, by Dave Mark (my co-author), Learn Objective-C on the Macintosh by Mark Dalrymple and Scott Knaster (an excellent new version that I've had the pleasure of tech reviewing), as well as two yet untitled books, one on Cocoa and one on Xcode.

Friday, October 3, 2008

Did you know you could take screenshots without Xcode?

I discovered this accidentally today. It may be documented somewhere, but I was not aware of it. You can take screenshots of your iPhone and store them in your iPhone's photo library, even if your phone is not hooked up to your Mac. I assume most people know that they can take screenshots using the Organizer in Xcode, but you can do it with just the iPhone and nothing else. I wish I would have known this when I was taking screenshots for the book.

Here's how you do it. Hold down the power button - the one that's on the top edge of the phone. While the power button is being held down, press and then quickly release the Home button (the round button with a rounded square on the front of the phone). You'll hear the click noise and see a flash, and when you go to the Photos application, you'll see your screenshot.

A Bit About the Responder Chain

Yesterday's post about handling double-taps provoked a question about how to handle double-taps using a UIWebView. I haven't worked much with UIWebView, but I think a little explanation of the way the responder chain works on the iPhone may help; it's a little different than the responder chain on Mac OS X.

Controllers are now officially part of the responder chain. Any event goes first to the First Responder, as you might expect.

If the First Responder (which is usually the UI element being interacted with) doesn't consume the event, it is not always passed directly up to the superview, as it is on OS X. Rather the First Responder checks to see if it has a controller, and if there is one, it does a lateral pass over to it. This gives the controller class the opportunity to respond to and/or consume events before it is passed up to the superview. This is why you can implement methods like touchesBegan:withEvent: on either a view or a view controller.

This gives you two options if you need to intercept events normally handled by a UIKit object, like the UIView: You can implement the touchesBegan:withEvent: either on the object's controller, or you can create a subclass of the object and implement the method there.

I don't know which should be used with UIWebView because I don't know if UIView consumes the double tap event. I'm guessing it does (I'll update if I get confirmation of this), so my guess is that you would have to subclass UIWebView to intercept double-taps. If it doesn't consume the event, then you could just intercept it in the controller class for the web view.

Whoah - made a little mistake in the original posting. When implementing this code in a controller class, you want to forward to the next responder. When subclassing an existing view that handles touches, you want to pass to super! I've corrected the post below to reflect the difference

Here's the trick, though. Implementing a method like touchesBegan:withEvent, by default, consumes that event so that it goes no further through the Responder Chain. However, if you're intercepting an event for a control that detects touches or gestures, then you need to make sure that you pass the event down the responder chain manually if you don't handle it completely.

Here is how you might intercept a double-tap in your controller class, letting any events that are not handled by your method proceed down th responder chain:

-(void)respondToFictionalEvent:(UIEvent *)event {
if (someCondition)
[self handleEvent:event];
[self.nextResponder respondToFictionalEvent:event];

When subclassing an existing view than has touch-handling code, you have to handle it a little differently. What you have to do instead, is to pass the unhandled event up to super, like so:

-(void)respondToFictionalEvent:(UIEvent *)event {
if (someCondition)
[self handleEvent:event];
[super respondToFictionalEvent:event];

Basically, if you don't want to consume the event, you have to manually call the same method on the next responder. That's it. That's the magic that lets you intercept some, but not all, events for an existing object. So, to intercept a double-tap in a subclass of UIWebView, you might do something like this:

Header: MyUIViewSubclass.h

#import <UIKit/UIKit.h>

@interface MyUIViewSubclass : UIView {



Implementation: MyUIViewSubclass.m

#import "MyUIViewSubclass.h"

@implementation MyUIViewSubclass

- (void)touchesBegan:(NSSet *)touches
withEvent:(UIEvent *)event {

UITouch *touch = [touches anyObject];
NSUInteger tapCount = [touch tapCount];
BOOL consumed = NO;

if (tapCount == 2) {
// Do whatever...
consumed = YES;

if (!consumed)
[super touchesBegan:touches withEvent:event];


Note - this is not tested code, but it should give you an idea of how the process works. This is the basic process you would use any time you need to intercept some, but not all, responder chain events.

Thursday, October 2, 2008

Handling Double Taps

Alright, since the NDA is down, let's celebrate by posting some information, shall we?

One question that I see posted a lot by new iPhone developers is "how do I handle double-taps?" The problem is that a double tap calls touchesBegan:withEvent: twice. If you want to have a different method called for a single-tap then a double-tap (in other words, if there's a double-tap, you don't want the single-tap method to fire), how do you handle it?

The answer lies in first using performSelector:withObject:afterDelay: to call the single-tap method after a delay that's short enough not to be noticed by the user, but long enough that the second tap of the double-tap will arrive before it actually executes. Then when the double-tap comes into touchesBegan:withEvent:, you use a little-known NSObject method called cancelPreviousPerformRequestsWithTarget:selector:object: to cancel the previous single-tap method call before calling the double-tap method.

Heres a code snippet that shows how to handle up to a quadruple-tap, with each number of taps resulting in a different method getting called.

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
NSUInteger tapCount = [touch tapCount];

switch (tapCount) {
case 1:
[self performSelector:@selector(singleTapMethod) withObject:nil afterDelay:.4];
case 2:
[NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(singleTapMethod) object:nil];
[self performSelector:@selector(doubleTapMethod) withObject:nil afterDelay:.4];
case 3:
[NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(doubleTapMethod) object:nil];
[self performSelector:@selector(tripleTapMethod) withObject:nil afterDelay:.4];
case 4:
[NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(tripleTapMethod) object:nil];
[self quadrupleTap];


Ego Boost

I don't put too much faith in their ranking system, but I must admit that it feels good that our book has shot up in the Amazon rankings. A few weeks ago, we were ranked in the #12,000 range, before the NDA dropped, we had moved up to about #4,000, and since the NDA drop, we've shot up to a whopping #1,404 in the overall ranking for all books (or thereabouts, it changes constantly). Nearly half the people visiting the Amazon page for our book are ordering it, and we're the #2 book in several relevant categories.

I have no idea what this means in terms of pre-orders, but it does give me the warm-fuzzies. Last time I checked, our book was the highest ranked of any of the iPhone SDK books, and the competition is not exactly lightweight. I'd be thrilled to even be running a close second to some of the other planned iPhone SDK books.

I'm hoping to have a publication date soon. The production side of the book has been on the back burner because of the NDA. Now that it's been lifted, we're in hurry-hurry-rush-rush mode, but I don't think the October 27th date is going to happen. Hopefully we won't miss by much, though. When I know more, I'll post more.

It's been a long haul, but the book has given me the opportunity to work with some really great people. Thanks to everyone who has offered their kind words of support (and those who e-mailed me that the NDA had been dropped).

Wednesday, October 1, 2008

Holy %@#$!

It looks like Apple finally decided on a course change. This morning, they dropped the NDA. The timing couldn't be much better, as the book is almost ready to go to press. We've got a few comments from the production people to address in a few chapters, and then a final review of the bluelines, and then it's off to the printer.

I'm so happy, I'm practically giddy. Up until just a few days ago, we were hearing from people inside Apple that they didn't think it was likely that the NDA would drop any time soon.

It's like Christmas came early for me.