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PODo I have to specify a protocol if I want my class to have a delegate?
 

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  1. PODo I have to specify a protocol if I want my class to have a delegate?
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    <p>I'm new to Objective-C and development on Apple's platforms, but hopefully I can frame this question in an understandable way regardless :)</p> <p>I want to parse an XML feed for my iPhone app, and I decided instead of shoving all of the delegation methods from an instance of NSXMLParser into my view controller, I'd wrap this up inside of a FeedParser class. After reading a few docs and example code, here's what I came up with:</p> <pre><code>@protocol FeedParserDelegate &lt;NSObject&gt; - (void)parserDidLoadEpisodes:(NSArray *)episodes; @end @interface FeedParser : NSObject { id &lt;FeedParserDelegate&gt; delegate; } @property (nonatomic, assign) id &lt;FeedParserDelegate&gt; delegate; - (id)initWithURL:(NSURL *)url delegate:(id&lt;FeedParserDelegate&gt;)theDelegate; @end </code></pre> <p>Simple. Delegates of my FeedParser object just have to implement <code>parserDidLoadEpisodes</code>.</p> <p>However, as I started actually making my <code>FeedParser</code> class use <code>NSXMLParser</code>, I realized that I didn't have to specify that <code>FeedParser</code> implements a protocol for <code>NSXMLParser</code> -- I could just implement the delegate methods that I wanted to do something with. I think I've noticed this with other classes that follow the delegate pattern, too, but not all.</p> <p>So why wouldn't I too just not bother with specifying a formal protocol for my <code>FeedParser</code> class? It would cut away some perhaps unnecessary code. I guess the question is: why would I <em>want</em> to create a formal protocol instead of just doing something like just checking to see if the method is implemented on the delegate with <code>respondsToSelector</code>? Is it only so that the compiler will issue nice warnings if a required delegate method isn't implemented?</p>
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