title: Sorting NSString values as if NSInteger using NSSortDescriptor
body: <p>I have created a sort descriptor to sort a plist response coming from my server. This works well with sort key having values upto 9. With more than 10 items I see abrupt results with sort key arranged in the order = 1, 10, 11, 2, 3, 4, 5, 6, 7, 8, 9</p>
  
  <pre><code>NSSortDescriptor *aSortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"sort" ascending:YES];
  self.myList = [NSMutableArray arrayWithArray:[unsortedList sortedArrayUsingDescriptors:[NSArray arrayWithObject:aSortDescriptor]]];
  </code></pre>
  
  <p>How to make it arrange in the correct order of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11?</p>