Question

I create two mutable arrays – referenceArray & stemArray, I then fill the referenceArray with URLs. I’d like to make stemArray an exact copy of referenceArray. I gather that making
the assignment stemArray = referenceArray; is not correct (strange things happen when I try this). There must be a better way then simply creating a second loop & filling up stemArray that way? I’m still not very comfortable with pointers & I believe this situation is a potential minefield…any hints or suggestions? thanks in advance 🙂

    referenceArray = [NSMutableArray arrayWithCapacity:numberOfStems];
    referenceArray = [[NSMutableArray alloc] init];

    stemArray =  [NSMutableArray arrayWithCapacity:numberOfStems];
    stemArray =  [[NSMutableArray alloc] init];

for ( int i = 1; i <= numStems; i++ ) {
    NSString *soundName = [NSString stringWithFormat:@"stem-%i", i];
    NSString *soundPath = [[NSBundle mainBundle] pathForResource:soundName ofType:@"mp3"];
    NSURL *soundFile = [[NSURL alloc] initFileURLWithPath:soundPath];   
    [referenceArray addObject:soundFile];
}

Answer 1

You’re overwriting pointers to your mutable arrays immediately after you create them – why are those alloc/init lines in there? If you want a copy of an NSArray, just send it a copy message:

referenceArray = [NSMutableArray arrayWithCapacity:numberOfStems];

for ( int i = 1; i <= numStems; i++ ) {
    // Fill in referenceArray
}

stemArray = [referenceArray copy];