iOS and Automatic Reference Counting for Memory Management

strong "keep this in the heap until I don't point to it anymore"

• I won't point to it anymore if I set my pointer to it to nil.

• Or if I myself am removed from the heap because no one strongly points to me!

weak "keep this as long as someone else points to it strongly"

• If it gets thrown out of the heap, set my pointer to it to nil automatically (if user on iOS 5 only).
  

This is reference counting done automatically for you.

• Finding out that you are about to leave the heap

• A special method, dealloc, is called when your instance's memory is freed from the heap.

  • rarely ever have to implement this method. It's "too late" to do much useful here.
    - (void)dealloc
    {
          [[NSNotificationCenter defaultCenter] removeObserver:self];
    }