Re: [Pyobjc-dev] PyObjC equivalent of ObjC's categories?

[Bob I. <bo...@re...>]

On Oct 26, 2003, at 9:17 AM, Jacob Kaplan-Moss wrote:

> For me, one of the most powerful tools that ObjC gives is the ability 
> to create "categories" on existing classes.  This allows extending 
> existing classes without actually needing to subclass them.  For 
> example (taken from Apple's AnimatedSlider sample code):
>
> @interface NSSlider (SliderAnimation)
>
> - (IBAction) animateToFloatValueFrom: sender;
> - (void) animateToFloatValue:(float) newValue;
>
> @end
>
> The above adds two instance methods to the NSSlider used in the 
> application.
>
> How would I go about doing the same thing in PyObjC?  Obviously I 
> could subclass NSSlider to add the new methods, but I guess I'm 
> looking for something that's a closer functional match to what the 
> ObjC code does.

from the objc module:

Help on built-in function classAddMethods:

classAddMethods(...)
     classAddMethods(targetClass, methodsArray)

     Adds methods in methodsArray to class.   The effect is similar to 
how categories work.   If class already implements a method as defined 
in methodsArray, the original implementation will be replaced by the 
implementation from methodsArray.

I don't believe this is very well known, I had the same question as you 
yesterday, but I found the answer by reading through the PyObjC source 
code.

-bob