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POIs this a good way to do a game loop for an iPhone game?
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copied!<p>I'm new to iPhone dev, but trying to build a 2D game. I was following a book, but the game loop it created basically said:</p> <pre><code>function gameLoop update() render() sleep(1/30th second) gameLoop </code></pre> <p>The reasoning was that this would run at 30fps. However, this seemed a little mental, because if my frame took 1/30th second, then it would run at 15fps (since it'll spend as much time sleeping as updating).</p> <p>So, I did some digging and found the CADisplayLink class which would sync calls to my gameLoop function to the refresh rate (or a fraction of it). I can't find many samples of it, so I'm posting here for a code review :-) It seems to work as expected, and it includes passing the elapsed (frame) time into the Update method so my logic can be framerate-independant (however I can't actually find in the docs what CADisplayLink would do if my frame took more than its allowed time to run - I'm hoping it just does its best to catch up, and doesn't crash!).</p> <pre><code>// // GameAppDelegate.m // // Created by Danny Tuppeny on 10/03/2010. // Copyright Danny Tuppeny 2010. All rights reserved. // #import "GameAppDelegate.h" #import "GameViewController.h" #import "GameStates/gsSplash.h" @implementation GameAppDelegate @synthesize window; @synthesize viewController; - (void) applicationDidFinishLaunching:(UIApplication *)application { // Create an instance of the first GameState (Splash Screen) [self doStateChange:[gsSplash class]]; // Set up the game loop displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(gameLoop)]; [displayLink setFrameInterval:2]; [displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; } - (void) gameLoop { // Calculate how long has passed since the previous frame CFTimeInterval currentFrameTime = [displayLink timestamp]; CFTimeInterval elapsed = 0; // For the first frame, we want to pass 0 (since we haven't elapsed any time), so only // calculate this in the case where we're not the first frame if (lastFrameTime != 0) { elapsed = currentFrameTime - lastFrameTime; } // Keep track of this frames time (so we can calculate this next time) lastFrameTime = currentFrameTime; NSLog([NSString stringWithFormat:@"%f", elapsed]); // Call update, passing the elapsed time in [((GameState*)viewController.view) Update:elapsed]; } - (void) doStateChange:(Class)state { // Remove the previous GameState if (viewController.view != nil) { [viewController.view removeFromSuperview]; [viewController.view release]; } // Create the new GameState viewController.view = [[state alloc] initWithFrame:CGRectMake(0, 0, IPHONE_WIDTH, IPHONE_HEIGHT) andManager:self]; // Now set as visible [window addSubview:viewController.view]; [window makeKeyAndVisible]; } - (void) dealloc { [viewController release]; [window release]; [super dealloc]; } @end </code></pre> <p>Any feedback would be appreciated :-)</p> <p>PS. Bonus points if you can tell me why all the books use "viewController.view" but for everything else seem to use "[object name]" format. Why not [viewController view]?</p>

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