Question

Is the following legal in Objective-c with ARC enabled?

NSMutableArray * smallArray = [[NSMutableArray alloc] initWithObjects:@"1", @"2", @"3", nil];
smallArray = [[NSMutableArray alloc] initWithObjects:@"4", "5", nil];

I thought it should be. However, in this situation it gives me EXEC_BAD_ACCESS on the forth line:

NSMutableArray * bigArray = [[NSMutableArray alloc] init];
NSMutableArray * smallArray = [[NSMutableArray alloc] initWithObjects:@"1", @"2", @"3", nil];
[bigArray addObject: smallArray];
smallArray = [[NSMutableArray alloc] initWithObjects:@"4", "5", nil];

addObject copies the pointer right? So if I allocate a new segment of memory to smallArray to point to, what is wrong with that?

However this code segment does not crash:

NSMutableArray * bigArray = [[NSMutableArray alloc] init];
NSMutableArray * smallArray = [[NSMutableArray alloc] initWithObjects:@"1", @"2", @"3", nil];
[bigArray addObject: smallArray];
smallArray = [[NSMutableArray alloc] init];
[smallArray addObject:@"4"];
[smallArray addObject:@"5"];

What’s going on here?

Answer 1

Try this:

smallArray = [[NSMutableArray alloc] initWithObjects:@"4", "5", nil];

The second object must be @”5″, not just “5”.