Re: question about informal protocols
Re: question about informal protocols
- Subject: Re: question about informal protocols
- From: Jean-Daniel Dupas <email@hidden>
- Date: Fri, 20 Nov 2009 20:57:30 +0100
Le 20 nov. 2009 à 20:46, Michael de Haan a écrit :
> I am working through an example in Buck/Yacktman's book that uses an informal protocol.
>
> In the interface of of a custom class, it is declared as such.
>
>
> #import <Cocoa/Cocoa.h>
>
>
> @interface MyShapeEditorDocument : NSDocument
> {
> ....ivars....
> }
> @end
>
>
> @interface NSObject(MYShapeEditingDocEditor)
>
>
>
> -(void) controllerDidEndEditing;
> @end
>
>
> In the implementation file it is defined, twice, thus.
>
>
> @implementation NSObject(MYShapeEditingDocEditor)
>
> -(void) controllerDidEndEditing
> {
>
> }
> @end
>
> and in the main body of the code, thus.
>
>
> @implementation MyShapeEditorDocument
>
>
> -(void) controllerDidEndEditing
> {
> [[self myView] setNeedsDisplay: YES];
> [[self table] reloadData];
> }
>
>
> Apple's docs say: "When used to declare a protocol, a category interface doesn’t have a corresponding implementation. Instead, classes that implement the protocol declare the methods again in their own interface files and define them along with other methods in their implementation files." (http://developer.apple.com/mac/library/documentation/cocoa/Conceptual/ObjectiveC/Articles/ocProtocols.html#//apple_ref/doc/uid/TP30001163-CH15-TPXREF147)
>
>
> What I am not following is the seemingly double definitions. From the docs, it would seem that implementation is a 2 step process, not a 3 step as above, even though this is clearly correct. What is the essence that I am missing?
The usual way is to NOT implements the NSObject category and test if the delegate implements the method using -respondsToSelector:
But this way works too if you don't want to have to test before sending your message.
Anyway, informal protocols are "deprecated" in favor of @protocol with @optional method.
-- Jean-Daniel
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