CODEWITHSUNDEEP
objective-cios
Joel Derfner
Joel Derfner

Reputation: 2207

how to make methods in category classes available to other classes?

I want to use a class I got from iosframeworks.com called UIImage+ProportionalFill. I know it's a category extending UIImage, but when I try to use one of its methods in another class I get a message saying no visible @interface for UIImage declares the selector 'nameOfWhateverMethodIWantToUse'. I'm not surprised to get an error, since there must be more to using it than dropping it into XCode, but how do I make the methods in the new category/class available to other classes?

Upvotes: 1

Views: 146

Answers (4)

bs7
bs7

Reputation: 627

Based on what you said, I think you just forgot to import it.

#import "UIImage+ProportionalFill.h"

Write it on the top of the .h file of the class where you want to use the method.

Upvotes: 2

bbum
bbum

Reputation: 162722

You need to #import the header containing the method declaration(s) in each file that uses said methods.

Note tha the methos should be prefixed; i.e. -JDnameOfWhateverMethodIWantToUse.

Note also that adding categories to framework classes willy nilly can easily lead to a rather awfully architected application that becomes difficult to refactor/maintain.

Upvotes: 2

jscs
jscs

Reputation: 64022

The compiler needs to be able to see the declaration of the methods, which should be in the category's header file. You must import the header file wherever you want to use the methods.

Upvotes: 2

Frank
Frank

Reputation: 15661

You just need to import your category in the class you like to use it...

#import "UIImage+ProportionalFill.h"

I usually do this in the header file.

Upvotes: 4

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