Why can't I initialize getter this way in Objective C?

Question

I'm a bit confused why I can't initialize a getter this way:

@synthesize stack = _stack;

- (NSMutableArray *) stack
{
    if (self.stack == nil) {
        self.stack = [[NSMutableArray alloc] init];
    }
    return self.stack;
}

I know that if I replace self.stack with _stack, it will work perfectly fine, but I just don't know why I can't use self.stack. I use self.stack later on in the code without problem though.

Answer 1

The problem is in following line:

if (self.stack == nil) 

which is equivalent to

if ([self stack] == nil)

So you're calling your getter method inside itself and that results in infinite recursion. You can remove calling the getter by addressing the ivar itself:

- (NSMutableArray *) stack
{
    if (_stack == nil) {
        _stack = [[NSMutableArray alloc] init];
    }
    return _stack;
}