title: Objective-C - How to compare arrays and extract the difference?
body: <blockquote>
    <p><strong>Possible duplicate</strong>: <a href="https://stackoverflow.com/questions/1475636/comparing-two-arrays/1475656#1475656">comparing-two-arrays</a></p>
  </blockquote>
  
  <p>I have two NSArray and I'd like to create a new Array with objects from the second array but not 
  included in the first array.</p>
  
  <pre><code>Example:
  
  NSMutableArray *firstArray = [NSMutableArray arrayWithObjects:@"Bill", @"Ben", @"Chris", @"Melissa", nil];
  NSMutableArray *secondArray = [NSMutableArray arrayWithObjects:@"Bill", @"Paul", nil];
  
  The resulting array should be: 
  
  [@"Paul", nil];
  </code></pre>
  
  <p>I solved this problem with a double loop comparing objects into the inner one.</p>
  
  <p>Is there a better solutions ?</p>