CODEWITHSUNDEEP
objective-c
Thanks
Thanks

Reputation: 40329

How does a category work?

I'm new to objective-c and need to extend a standard class of a framework with an instance variable plus accessors. I heard that this is done with a so called "category", which sounds pretty confusing to me. How does this basically work?

Upvotes: 5

Views: 2983

Answers (2)

Don McCaughey
Don McCaughey

Reputation: 9982

A category adds methods to the table of methods inside a class. It's very handy for adding application specific methods to existing framework classes.

If you need to add instance variables to a class, a category won't do the job -- categories only add methods, not data. To add instance variables, you must subclass.

Upvotes: 11

mouviciel
mouviciel

Reputation: 67829

A category of a class adds methods to that class. It cannot add instance variables.

If you need to add instance variables you may want to subclass instead.

Upvotes: 7

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