title: IOS sort NSMutableArray for a numeric field
body: <p>I hope that there is somebody outside, who can help me with this:</p>
  
  <p>I have an unsorted array of dictionaries which have a STRING field (Km) inside that contains numbers (e.g. 12,0; 1,2; 6,4). If I do a normal SORT, the array will be sorted that way:
  1,2
  12,0
  6,4</p>
  
  <p>But it should sorted that way:
  1,2
  6,4
  12,0</p>
  
  <p>Does anybody has an example code how to do this? 
  I'm looking forward to get an answer.</p>
  
  <p>Thanks and regards
  Marco </p>
  
  <p>Edit my code for further understanding:</p>
  
  <pre><code>NSMutableArray *tempArray = [[NSArray alloc] init];
  self.Digger = tempArray;
  [tempArray release];
  
  self.Digger = [self.Diggers objectForKey:@"Rows"];
  
  NSSortDescriptor * sort = [[[NSSortDescriptor alloc] initWithKey:@"KM" ascending:true] autorelease]; [self.Digger sortUsingDescriptors:[NSArray arrayWithObject:sort]];
  self.Digger = sort;
  </code></pre>
  
  <p>But this gives me the follwoing error in the log:
  -[NSSortDescriptor count]: unrecognized selector sent to instance </p>