Add Sound to Your Game - Beginning iOS6 Games Development - page 258

Listing 11-7. prepareAudio: (GameController.m)
-(AVAudioPlayer*)prepareAudio:(NSString*)audioName{
if (audioNameToPlayer == nil){
audioNameToPlayer = [NSMutableDictionary new];
}
NSURL *url = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:audioName
ofType:@"m4a"]];
AVAudioPlayer* player = [[AVAudioPlayer alloc] initWithContentsOfURL:url error: nil];
[player prepareToPlay];
[audioNameToPlayer setValue:player forKey: audioName];
return player;
}
In Listing 11-7, we see the task prepareAudio :. This task is responsible for creating an AVAudioPlayer
for each audio file passed in. We do this by first lazily initializing an NSMutableDictionary called
audioNameToPlayer , which maps the NSString audioName to an AVAudioPlayer once constructed. To
create an NSAudioPlayer , we first create an NSURL pointing to the desired m4a file in the project. To
construct the NSAudioPlayer, we simply call initWithContentsOfURL:error: , ignoring any error.
We call prepareToPlay on the newly created player in order to make sure that the file is loaded and
ready to make sound as soon as we call play on it sometime later.
The other sound-related task called in our doSetup task, from Listing 11-5, is playBackgroundAudio :,
which is shown in Listing 11-8.
Listing 11-8. playBackgroundAudio: (GameController.m)
-(void)playBackgroundAudio:(NSString*)audioName{
if (backgroundPlayer != nil){
[backgroundPlayer stop];
}
backgroundPlayer = [self prepareAudio:audioName];
[backgroundPlayer setNumberOfLoops:-1];
if (!otherAudioIsPlaying){
[backgroundPlayer play];
}
}
In Listing 11-8, the task playBackgroundAudio : takes the name of an audio file. If an existing
AVAudioPlayer backgroundPlayer exits, we stop it. Next, we call prepareAudio: to construct
and initialize an AVAudioPlayer . To make the audio play indefinitely, we call setNumberOfLoops:
and specify −1. While we want the background audio to play continuously, we can instead
use setNumberOfLoops: to play an audio file a fixed number of times. The naming of the task
setNumberOfLoops: is a little weird; it indicates the number of extra times a track is played. So,
for example, if you specified 0, the audio would play once (the default number of times). If you
specified 3, the audio track would play 4 times. Basically, setNumberOfLoops: specifies the number
of additional times the audio should be played.