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Official Forum for Programming in Objective-C (the iPhone Programming Language) - Stephen Kochan
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Chapter 11 - Categories and Protocols
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Category in Library
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Topic: Category in Library (Read 1773 times)
rhildreth
Newbie
Posts: 4
Category in Library
«
on:
September 13, 2011, 09:44:50 AM »
I've placed the MathOps category from Program 11.1 in its own files (Fraction+MathOps.h & .m) which works fine but the compiler complains that it can't find the methods (add:, etc.) unless I import Fraction+MathOps. On p. 224 is this: "If you don’t have the capability to modify the
original header file directly (consider adding a category to an existing class from a
library, as shown in Part II,“The Foundation Framework”),". I can't seem to find an explanation on how to add a category to an existing class from a library.
Anyone have some suggestions on how to do this?
Thanks.
Ron
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skochan
Administrator
Hero Member
Posts: 3114
Re: Category in Library
«
Reply #1 on:
September 13, 2011, 10:16:12 AM »
Ron,
It's easy to add a category to an existing class. Just import Foundation.h and then add your class extension. For example:
Code: (Objective-C)
#import <Foundation/Foundation.h>
@interface NSString (customPaths)
...
@end
adds a category called customPaths to the NSString class. See page 360 for an example of how a category called Printing is added to the NSSet class.
Cheers,
Steve
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rhildreth
Newbie
Posts: 4
Re: Category in Library
«
Reply #2 on:
September 13, 2011, 08:22:38 PM »
Thanks - I understand that.
It's the "adding a category to an existing class from a library" procedure that I was looking for.
Ron
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