title: Cancel Selector in UITableViewCell
body: <p>I have scenario that in which i am using selector in TableViewCell as bellow and when I click on back button in my view I want to cancel that selector and I am sending dictionary as object in Selector </p>
  
  <p>My code is as bellow</p>
  
  <p><strong>In Header File</strong></p>
  
  <pre><code> NSMutableDictionary* photoDict;
   NSMutableDictionary* dictImages;
  </code></pre>
  
  <p><strong>In .M file</strong></p>
  
  <pre><code>-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
  {
      NSString *cellIdentifier = @"Cell";
  
      UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
      if(cell==nil)
      {
          cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:cellIdentifier];
          [[NSBundle mainBundle]loadNibNamed:@"MyCellNib" owner:self options:Nil];
          cell = detailChainObj;
      }
  
      NSString* avatarURL =@"image_Url"; //Any url of image for cell.
      NSString *key =[[NSString alloc] initWithFormat:@"Key%d%d",indexPath.section,indexPath.row];
  
      dictImages = [NSDictionary dictionaryWithObjectsAndKeys:imageViewCell,@"Img",imgURL,@"imgURL",key,@"key", nil];
      [self performSelectorInBackground:@selector(DownloadLinkzImageOfUser:) withObject:dictImages];
  
  
      if([photoDic valueForKey:keyAvt])
      {
          NSData* data = (NSData*)[photoDic valueForKey:key];
          imageViewCell.image = [UIImage imageWithData:data];
      }
      else
      {
          [self performSelectorInBackground:@selector(DownloadImagesForCell:) withObject:dictImages];
      }
  }
  
  
  //
  
  -(void)DownloadImagesForCell:(NSDictionary *)result
  {
      UIImageView* img = (UIImageView*)[result objectForKey:@"Img"];
      NSString* urlAvt = [result valueForKey:@"imgURL"];
      if([urlAvt isEqualToString:@"No Image"])
      {
         img.image = [UIImage imageNamed:@"noimg.png"];
      }
      else
      {
         NSData* data = [NSData dataWithContentsOfURL:[NSURL URLWithString:imgURL]];
         img.image = [UIImage imageWithData:data];
         [photoDic setValue:data forKey:[NSString stringWithFormat:@"%@",[result valueForKey:@"key"]]];
      }
   }
  </code></pre>
  
  <p>Now I want to cancel this selecter when I press back button </p>
  
  <p>and please keep in mind that I have already use </p>
  
  <pre><code>[NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(DownloadImagesForCell:) object:dictImages];
  </code></pre>