Re: Trying to understand -- please help...

FROM : Andy Lee
DATE : Wed May 21 21:41:17 2008

On May 21, 2008, at 3:14 PM, Vijay Malhan wrote:
> Thanks for the pointers to the documentation. This is sample snippet 
> from
> the documentation.
>
> @implementation MyClass
>
> + (void)initialize
>
> {
>
>  if ( self == [MyClass class] ) {
>
>      /* put initialization code here */
>
>  }
>
> }
>
>
> If I'm not wrong "self" equivalent of "this" which points to an 
> instance
> var.


Not quite; "self" refers to the receiver of the +initialize message. 
Since +initialize is a class method, the receiver is a class.

Suppose you have a subclass of MyClass called MySubclass, and 
MySubclass doesn't implement its own version of +initialize.  When 
MySubclass receives the +initialize message, it will run the inherited 
+initialize method.  But then that method will get called twice: once 
for MySubclass and once for MyClass.  The above code shows how to 
avoid this (if you want to avoid it).

This is explained in the paragraph preceding this code snippet, but I 
thought I'd try to spell it out a bit.

--Andy