title: Issue with UITextfield into a NSMutableArray
body: <p>I had this working using NSArray until I realize I need to insert a string into array. Now I'm changing this to a NSMutableArray, but having issues with my syntax. Am I allowed to use componentsJoinedByString in NSMutable arrays?</p>
  
  <pre><code>    NSString *item;
      int numofSeg;
      int needSeg;
  if (textfield.text == @"::") {
          numofSeg = 0;
  
      }
      NSMutableArray *dlist = [[NSMutableArray alloc]init];
      //take string from textfield and split it into a list on colons.
      dlist = [textfield.text componentsSeparatedByString:@":"];
      //run through list to count how many segments. Non blank ones.
      for (item in dlist) {
          if (item != @""){
              numofSeg = numofSeg + 1;
              NSLog(@"%@",numofSeg);
          }
      }
      //determine number of segments
      needSeg = 8 - numofSeg;
      while (needSeg &gt; 0) {
          //insert 0000 at blank spot
          [dlist insertString:@"0000" atIndex:@""];
          needSeg = needSeg - 1;
      }
      for (item in dlist) {
          if (item == @"") {
              //remove blank spaces from list
              [dlist removeAllObjects:item];
          }
      }
      //join the list of times into a string with colon
      NSString *joinstring = [dlist componentsJoinedByString:@":"];
      NSLog(@"%@",joinstring);
  </code></pre>