title: How do I sort an NSMutableArray with custom objects in it?
body: <p>What I want to do seems pretty simple, but I can't find any answers on the web. I have an <code>NSMutableArray</code> of objects, and let's say they are 'Person' objects. I want to sort the <code>NSMutableArray</code> by Person.birthDate which is an <code>NSDate</code>.</p>
  
  <p>I think it has something to do with this method:</p>
  
  <pre><code>NSArray *sortedArray = [drinkDetails sortedArrayUsingSelector:@selector(???)];
  </code></pre>
  
  <p>In Java I would make my object implement Comparable, or use Collections.sort with an inline custom comparator...how on earth do you do this in Objective-C?</p>