Question

since every assignment to a variable with a different object increases its retain count and in the dealloc its not always clear how often a variable got assigned a simple [maVar release] might NOT BE SUFFICIENT. So using ALWAYS myVar = nil sets the retain count to zero, and a subsequent [myVar release] will never cause a problem again. (is it actually still required ?)

The only situation when not to do it this way is if myVar is passed OUT then I must not do this, since the value gets destroyed by myVar = nil;

Is my thinking correct? Or could this way of avoiding leaks cause any other problems?

Answer 1

Your thinking is incorrect in quite a lot of ways. These are probably just scratching the surface:

• Assignment to a variable does not increase its retain count. (There are some subtleties to do with properties, but frankly that’s way beyond the level we’re at here.)
• dealloc is called when the retain count reaches 0.
• Setting myVar = nil does not affect the retain count.
• myVar = nil destroys only the local pointer value, it does not destroy an object that has been passed out.
• It is safe to call [myVar release] when myVar is nil, but it isn’t useful — it does nothing.
• Worrying about retain counts is always a mistake. Worry about what you own.

It is clear that your grasp of C pointers and Objective-C memory management is a bit lacking. I’d suggest doing some remedial C work before several thorough re-reads of the Memory Management docs.