overriding a method in a Category?

Question

is it possible to override a method as a category method ?

@implementation CCSprite (Utilities)

-(void)draw //its already a member of CCSprite but I wantto override it. but within a category
{
   [super draw];
   [self doSomethingExtra];
}
@end

purpose: preventing to copy-paste same codeblock for each drived CCMySprite class.thinking Just import and use.

You can create subclass of `CCSprite`, let's say `BetterSprite` and then all your derived sprite classes can inherit from `BetterSprite` instead of `CCSprite`. — Tricertops, Feb 07 '13 at 22:39
Try adding `-(void)dealloc` category method to NSObject and see how bad your app leaks :D — Jeremy, Feb 07 '13 at 22:47

score 4 · Accepted Answer · edited Jun 20 '20 at 09:12

4

No, this isn't suggested by Apple, it's undefined behavior if you do that. One of the two methods will be used in this case, and you can't know which one.

Avoid Category Method Name Clashes

Because the methods declared in a category are added to an existing class, you need to be very careful about method names.

If the name of a method declared in a category is the same as a method in the original class, or a method in another category on the same class (or even a superclass), the behavior is undefined as to which method implementation is used at runtime. This is less likely to be an issue if you’re using categories with your own classes, but can cause problems when using categories to add methods to standard Cocoa or Cocoa Touch classes.

edited Jun 20 '20 at 09:12

Community

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answered Feb 07 '13 at 22:34

Ramy Al Zuhouri

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I think the last imported header is the winner of usage of draw method ? – Zen Of Kursat Feb 07 '13 at 22:35
1

No the “winner” is decided during runtime. – Tricertops Feb 07 '13 at 22:37
Usually it's like this, but you cannot be sure of it. It's very discouraged. – Ramy Al Zuhouri Feb 07 '13 at 22:38
if I define a helper class.I've to re-define more than 8-10 same methods taken from superclass.(otherwise getting BAD_ACCESS error) so I dont wantto do that. I just wantto define an override method once and use in child classes when necessary. so, what would you preferring to me? – Zen Of Kursat Feb 07 '13 at 22:38
A subclass, that's the way I suggest. – Ramy Al Zuhouri Feb 07 '13 at 22:43
I know its not good idea. but a question never asked before.so now in library with your suggestions. – Zen Of Kursat Feb 07 '13 at 22:56
I haven't understood this last comment. – Ramy Al Zuhouri Feb 08 '13 at 01:20

overriding a method in a Category?

1 Answers1