Question

As a relative Objective-C beginner, I’m obviously still not grasping certain memory management rules. I can’t figure out how to make this not crash:

@interface MyClass { NSArray *playerArray4th; }

- (void) viewDidLoad { playerArray4th = [self getAudioPlayersForSoundFile:@"rimshot" ofType:@"aif"]; }

- (NSArray*) getAudioPlayersForSoundFile:(NSString*)soundFileName ofType:(NSString*)soundFileType {

    //code instantiating objects....

    NSArray *toRet = [[NSArray alloc] initWithObjects:toRetTickPlayer,toRetTickPlayerCopy,toRetTickPlayerCopy2,toRetTickPlayerCopy3, nil];
    return toRet;
}

Then later, in a different function:

NSArray *currentArray = playerArray4th;
[currentArray release];
currentArray = nil;
currentArray = [self getAudioPlayersForSoundFile:fileName ofType:ofType];

And it crashes when trying to access the array again:

- (void) playSound:(NSString*)soundType {

    AVAudioPlayer *currentPlayer;

    if ([soundType isEqualToString:@"4th"]) {
        if (playerArray4thCounter >= [playerArray4th count]) playerArray4thCounter = 0;
        NSLog(@"Playing from array: %@",playerArray4th);
        currentPlayer = [playerArray4th objectAtIndex:playerArray4thCounter];
        playerArray4thCounter++;
    }
}

Answer 1

Try to learn about properties and about using getters and setters. Don’t take shortcuts unless you know exactly what’s going on.

So define the playerArray4th property in your header file:

@property (nonatomic,retain) NSArray *playerArray4th;

And then in your .m file create getter/setter:

@synthesize playerArray4th;

Then, always use self.playerArray4th for assigning and getting the variable. The prior objects will be released when needed.

So this will not leak:

self.playerArray4th = [NSArray arrayWithObjects:@"text",@"text",nil];
self.playerArray4th = [NSArray arrayWithObjects:@"new array",@"text",nil];

because the second assignment releases the first array.

Furthermore, read about using autorelease. In short, if you alloc, copy or new, you should either release or autorelease. There’s a lot to read about this here on SO which I will not repeat here now.

Don’t forget to put self.playerArray4th = nil; in your dealloc method.