Question

I currently have some code that looks like:

-(UIView)someMethod {
  CGRectMake(0,0,100,100);
  UILabel *label = [[UILabel alloc] initWithFrame:rect];
  return label;
}

While it works it obviously leaks memory and needs to be fixed. I thought the fix would be:

UILabel *label = [UILabel initWithFrame:rect];

But the compiler tells me that UILabel doesn’t respond to initWithFrame. I guess my question is two-fold:

a) What is the correct way to do this so I’m not leaking memory?

and

b) I’m confused as to why [UILabel alloc] would respond to initWithFrame but not UILabel by itself (my understanding is that UILabel is inherited from UIView that does respond to initWithFrame).

Answer 1

a) You can’t avoid +alloc. But you can use -autorelease to relinquish the ownership.

-(UIView*)someMethod {
  CGRect rect = CGRectMake(0,0,100,100);
  UILabel *label = [[[UILabel alloc] initWithFrame:rect] autorelease];
  return label;
}

b) +alloc is a class method, and -initWithFrame: is an instance method. The latter can only be called on _{^{(or, in ObjC terminology, sent to)}} an instance of UILabel. However, the symbol “UILabel” is a class, not an instance, so [UILabel initWithFrame:rect] won’t work. Similarly, a class method like +alloc can only be called on a class, so [label alloc] won’t work.