Can a category implement a protocol in Objective C?

objective-c cocoa protocols categories
cfischer picture cfischer · Apr 28, 2011 · Viewed 16.5k times · Source

I have a category on NSDate and it would be convenient if it could implement a protocol I previously created. Is this possible? what's the correct syntax for this?

Answer

Nikolai Ruhe picture Nikolai Ruhe · Apr 28, 2011

Yes, that's possible. The syntax is:

@interface NSDate (CategoryName) <ProtocolName>
@end

@implementation NSDate (CategoryName)
@end

Here's Apple's documentation on the topic.

It's also possible to do this using a class extension. I very much like this to privately conform to delegate protocols. Doing so hides the implementation detail of being some delegate of some class from the public interface and removes the dependency from the header.

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