What does (void (^)(BOOL supported)) mean? : <p>as I am working myself into some new code, I came across a thing, where I couldnt find any explanation for in the web so far. So hopefully you can give me one.</p>

<p>I have this method signature in Objective-C code:</p>

<pre><code>-(void) supportsUrl: (NSString*) url callback:(void (^)(BOOL supported)) callback;
</code></pre>

<p>Can someone please tell me what it is about in the last parameter?</p>

<p>Thanks a lot!</p>
