Comments on: iPhone from A Game Developer’s Perspective: The iPhone API

By: Noel

Noel — Tue, 24 Feb 2009 16:25:18 +0000

There’s no need to get into undocumented stuff to turn off the selection bar in UIPickerView. Just turn the property showsSelectionIndicator to false and you’re all set

By: Jeshua Lacock

Jeshua Lacock — Tue, 24 Feb 2009 10:40:43 +0000

Hello Noel,

Is there anyway you could tell me what variable you used to disable the selection bar for the UIPickerView?

Thanks!

By: Noel

Noel — Mon, 19 Jan 2009 05:10:45 +0000

@Tim: I looked into accessing _pickerViewFlags from UIPickerView through valueForKey, but that was a no go. I was able to access the private variables OK, but somehow not that one (it would cause an unhandled memory access just to try and access it). I don’t know if it’s because it’s in the @package visiblity or what.

Then I tried to do a really horrible hack: Figure out where _pickerViewFlags is in memory (UIPickerView + 0x3C) and change it directly. Unfortunately, it looks like soundsEnabled is not really used! I can tweak some of the other variables, and turn off the selection bar for example, but the soundsEnabled bit is turned off already.

Thanks for the technique anyway, I’m sure it’s going to come in handy. Too bad it won’t solve this one problem.

By: Rod

Rod — Tue, 06 Jan 2009 04:25:37 +0000

Is there somewhere I can get a copy of the “Crash Landing,” source? It appears to be no longer available in the Apple Developers samples.

thanks

By: Tim

Tim — Tue, 06 Jan 2009 02:51:35 +0000

Regarding your issue with the UIPickerView sound flag, Objective-C doesn’t really have private variables. With Key Value Coding (KVC), you can get and set the value for any member variable. Use -valueForKey: and -setValue:forKey:. Now, you still might not want to do it since Apple could change the _pickerViewFlags structure at any time.

I recommend the new book Learn Objective-C on the Mac. It is a good, concise book that teaches cool ideas like this.

By: Rod

Rod — Mon, 05 Jan 2009 23:22:02 +0000

I think I tried STL as a test and it worked, and I also installed Boost and it works as well.

By: Noel

Noel — Mon, 05 Jan 2009 19:57:40 +0000

No way Michael! No way I’m writing another technical book any time soon. It’s such a thankless job and there’s hardly any money involved unless you’re targetting a huge audience.

By: Noel

Noel — Mon, 05 Jan 2009 19:55:34 +0000

Claus,

To tell you the truth, I hadn’t even looked into the STL. I don’t like it for runtime stuff, so I didn’t even think of looking. The template support in the iPhone compiler is a bit old, but I just checked and the STL headers are there and they compile and link just fine. One weird thing is that they aren’t in the std:: namespace but in _GLIBCXX_STD. WTF? :-b

Even if that wasn’t the case, I’m sure you could get STLPort or uSTL to work just fine.

As far as floating point support, is right there. The CPU has a hardware floating point unit, so performance is supposed to be decent.

I admit that I’m working on 100% iPhone exclusive apps though, so I’m not trying to keep them cross-platform. I was able to create a prototype in C++ and OpenGL on Windows and have it up and running on the iPhone with almost no changes though, so as long as you’re not doing iPhone-specific stuff, porting should be pretty easy.

By: Michael Seare

Michael Seare — Mon, 05 Jan 2009 19:08:39 +0000

“I hope that books and other resources pop up with that audience in mind.”

Hmmm… I smell another book you can write.

By: mos

mos — Mon, 05 Jan 2009 18:35:14 +0000

@Claus Hoefele

No stl? Yikes. That’s …not good. I’m going to have to refactor quite a bit of code later this week when I pick up my mini. (I naively thought I could write the C++ game engine in Visual Studio.)

By: Claus Hoefele

Claus Hoefele — Mon, 05 Jan 2009 10:34:01 +0000

Because you mentioned the fixed-function PowerVR chip: I wonder if you mostly use fixed-point math or if the iPhone is fast enough with floating-point calculations.

I find the lack of common basic types such as float and stl::vector makes it difficult to share code between game engines for Windows/Mac and smartphones.

Last time I looked, Wolfgang Engel’s Oolong Engine makes heavy use of floating-point math and he also uses USTL, see http://www.oolongengine.com/, but I somewhat doubt the performance beyond simple demos.

I’d be interested in reading your thoughts about cross-platform development or whether you see your iPhone games as completely separate implementations.

By: Eric Scrivner

Eric Scrivner — Mon, 05 Jan 2009 07:42:21 +0000

Great article, I’ve recently started Cocoa and iPhone development myself and it’s good to read the opinions of someone else as well. Keep the good articles a-comin’