title: Objective C - "Duplicate declaration of method" compilation error
body: <p>I have this piece of code:</p>
  
  <pre><code>- (id) getSearchSuggestions:(NSString*)q;
  - (NSOperationQueue*) getSearchSuggestions:(NSString*)q callback:(id&lt;UserDelegate&gt;)callback;
  - (id) getSearchSuggestions;
  - (NSOperationQueue*) getSearchSuggestions:(id&lt;UserDelegate&gt;)callback;
  </code></pre>
  
  <p>And I Xcode keeps showing me an error on the <strong>last</strong> line:</p>
  
  <pre><code>Duplicate declaration of method "getSearchSuggestions"
  </code></pre>
  
  <p>Why? It seems to me that the signatures are all different.</p>