title: sorting dictionary by child key
body: <p>I understand how to display a dictionaries sorted content by means of obtaining allKeys into an NSMutableArray, sorting the array and using it as an index into the dictionary, but....</p>
  
  <p>What if I want to sort the parent keys by one of their child keys?</p>
  
  <p>for example, a dictionary with parent keys @"8979", @"6754", @8776", @"9076" and so on have child key / value pairs like:</p>
  
  <p>@"pos", 8
  @"pos", 4
  @"pos", 10
  @"pos", 7</p>
  
  <p>and so on.</p>
  
  <p>I know how to sort the parent keys to be: @"6754", @"8776", @"8979", @"9076"</p>
  
  <p>but how to sort the parent keys based on their respective @"pos" child key resulting in:
  @"6754", @"9076", @"8979", @"8776"</p>
  
  <p>???</p>