title: TableViewCell don't reuse
body: <p>I use "Self Sizing Cells" in my tableview,when insert cell use 'insertRowsAtIndexPaths:withRowAnimation:'  cells will be dealloc sometime,but I have set reuseIdentifier for the cells. when I scroll the tableview, cells don't be dealloc.</p>
  
  <p>why for this?</p>
  
  <p>it's code I get cells:</p>
  
  <pre><code>Class cls = [CWNSessionUtil cellClassForContent:content];
          NSString *reuseIdentifier = [cls reuseIdentifier];
  
          cell = [tableView dequeueReusableCellWithIdentifier:reuseIdentifier];
          if(!cell)
          {
              cell = [[cls alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:reuseIdentifier];
          }
  
  
  +(Class)cellClassForContent:(id)content{
      Class cls;
  
      if([content isKindOfClass:[MessageEntity class]])
      {
          CubeMessageType type = [((MessageEntity *)content) type];
          switch (type) {
              case CubeMessageTypeFile:
                  cls = [CWNFileMessageCell class];
                  break;
              case CubeMessageTypeImage:
                  cls = [CWNImageMessageCell class];
                  break;
              case CubeMessageTypeVideoClip:
                  cls = [CWNVideoMessageCell class];
                  break;
              case CubeMessageTypeVoiceClip:
                  cls = [CWNAudioMessageCell class];
                  break;
              case CubeMessageTypeCustom:
                  cls = [self cellClassForCustomMessage:content];
                  break;
              default:
                  cls = [CWNTextMessageCell class];
                  break;
          }
  
      }
      else if([content isKindOfClass:[NSString class]])
      {
          cls = [CWNTipCell class];
      }
      else if([content isKindOfClass:[NSNumber class]])
      {
          cls = [CWNTimeCell class];
      }
      else
      {
          cls = [CWNTipCell class];
      }
  
      return cls;
  }
  </code></pre>