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copied!<p>The quick answer is: no, there is no way to have the compiler enforce the method signature of a method selector that is provided via a <code>SEL</code> argument.</p> <p>One of the strengths of Objective-C is that it is weakly-typed language, which allows for a lot more dynamic behaviour. Of course, this comes at the cost of compile-time type safety.</p> <p>In order to do what (I think) you want, the best approach is to use delegates. Cocoa uses delegates to allow another class to implement "callback"-type methods. Here is how it might look:</p> <blockquote> <p><strong>FooController.h</strong></p> </blockquote> <pre><code>@protocol FooControllerDelegate @required: - (void)handleData:(NSData *)data forFoo:(FooController *)foo; @end @interface FooController : NSObject { id <FooControllerDelegate> * delegate; } @property (assign) id <FooControllerDelegate> * delegate; - (void)doStuff; @end </code></pre> <blockquote> <p><strong>FooController.m</strong></p> </blockquote> <pre><code>@interface FooController (delegateCalls) - (void)handleData:(NSData *)data; @end @implementation FooController @synthesize delegate; - (id)init { if ((self = [super init]) == nil) { return nil; } delegate = nil; ... return self; } - (void)doStuff { ... [self handleData:data]; } - (void)handleData:(NSData *)data { if (delegate != nil) { [delegate handleData:data forFoo:self]; } else { return; // or throw an error // or handle it yourself } } @end </code></pre> <p>Using the <code>@required</code> keyword in your delegate protocol will prevent you from assigning a delegate to a <code>FooController</code> that does not implement the method exactly as described in the protocol. Attempting to provide a delegate that does not match the <code>@required</code> protocol method will result in a compiler error.</p> <p>Here is how you would create a delegate class to work with the above code:</p> <pre><code>@interface MyFooHandler <FooControllerDelegate> : NSObject { } - (void)handleData:(NSData *)data forFoo:(FooController *)foo; @end @implementation MyFooHandler - (void)handleData:(NSData *)data forFoo:(FooController *)foo { // do something here } @end </code></pre> <p>And here is how you would use everything:</p> <pre><code>FooController * foo = [[FooController alloc] init]; MyFooHandler * fooHandler = [[MyFooHandler alloc] init]; ... [foo setDelegate:fooHandler]; // this would cause a compiler error if fooHandler // did not implement the protocol properly ... [foo doStuff]; // this will call the delegate method on fooHandler ... [fooHandler release]; [foo release]; </code></pre>

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