Objective-C : Properties question

As far as I understand when you use properties the compiler still converts them to accessor methods during compilation. I got a little irritated when I read you need OSX 10.5 or later to use properties. Why is that so?

If in the compiled application are in fact still accessor methods I see no need fo开发者_如何学Pythonr OSX 10.5. Or is there something else going on during run-time?

Because the Objective-C 2.0 runtime was not back ported to 10.4. You need compiler and runtime support to handle all of ObjC 2.0 properly.