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PORequiring the presence of a method in an id
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  1. PORequiring the presence of a method in an id
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    copied!<h2>The Situation</h2> <p>My custom controller class has the following method:</p> <pre><code>- (void)requestViewControllerWithIdentifier:(NSString *)identifier fromObject:(id)object; </code></pre> <p>This causes <code>object</code> to receive this message:</p> <pre><code>- (UIViewController *)viewControllerWithIdentifier:(NSString *)identifier; </code></pre> <hr> <h2>The Problem</h2> <p>Right now, <code>object</code> is just an <code>id</code> so there's no guarantee that it actually implements that method, and I get a compiler warning when I send the message.</p> <hr> <h2>The Solution</h2> <p>I came up with two solutions myself:</p> <ol> <li>Use a protocol.</li> <li>Make <code>id</code> an <code>NSObject</code> and create a category for <code>NSObject</code>.</li> </ol> <p>They are both fine solutions probably and I don't mind choosing one of them, but...</p> <hr> <h2>The Question</h2> <p>...I noticed Apple is doing something odd in their GameKit API. <code>GKSession</code> has the following method:</p> <pre><code>- (void)setDataReceiveHandler:(id)handler withContext:(void *)context </code></pre> <p><code>handler</code> is just an <code>id</code>, but Apple actually requires it to implement this method:</p> <pre><code>- (void) receiveData:(NSData *)data fromPeer:(NSString *)peer inSession: (GKSession *)session context:(void *)context; </code></pre> <p>Without making use of any protocol or category! I'm wondering how and why would they do this? Why don't use a protocol? Do they enforce the method in some other way? If I were to do this, how can I suppress the compiler warning?</p>
 

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