title: causing a leak via performSelector with NSSelectorFromString?
body: <p>I am trying to have a fairly dynamic api for the level class of my game...  basically, I just have a bunch of class methods optionsForLevel1, optionsForLevel2, ...etc, that all return a dictionary object with things like how much time the level should have, how many bonus points, the level's name, etc...</p>
  
  <p>In my actual game object, when it's time to advance levels, it calls a method on the level object which does:</p>
  
  <pre><code>+(NSDictionary*)performClassSelectorForLevel:(int)identifier {
      SEL sel = NSSelectorFromString([NSString stringWithFormat:@"optionsForLevel%d", identifier]);
      return [self performSelector:sel];
  }
  </code></pre>
  
  <p>This gives me a warning:  PerformSelector may cause a leak because its selector is unknown.</p>
  
  <p>...</p>
  
  <p>How can I resolve this warning?</p>