NSMutableArray containsObject method not detecting object

Question

// Add the button to the NSMutableArray.
...
UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
[[self hBtns] addObject:btn];
...

// In another method, try to see if it exists.
- (void)didPushBtn:(id)sender
{
  UIButton *btn = (UIButton *)sender;
  if ([[self hBtns] containsObject:btn]) // Is false every time.
  ...
}

Why is it not detecting that the UIButton is in the array?

---

EDIT

It turns out that it won't even detect it right after it's added:

UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
[[self hBtns] addObject:btn];
if ([[self hBtns] containsObject:btn]) // Returns false.

Answer 1

Sounds like the isEqual: comparison is failing. Can you take a look at the hash for the UIButton in both places (where it's added, and then in didPushBtn) and see if they're the same value?

Answer 2

I had forgotten to initialize the array (*doh*):

[self setHBtns:[[NSMutableArray alloc] initWithCapacity:0]];