title: adding KVO to UITableViewCell
body: <p>I have a custom UITableViewCell which is displaying various attributes of a Person object (backed by Core Data) ... some labels, images etc. I currently force the whole tableview to reload whenever any property changes, and that's obviously not efficient. I know with KVO, I should be able to add a listener to a label in the cell that can listen for changes in the Person's properties. But I'm not sure how to implement it and can't find any examples. </p>
  
  <p>Here's what I typically do in my UITableView's cellForRowAtIndexPath:</p>
  
  <pre><code>    - (UITableViewCell *) tableView: (UITableView *) tableView cellForRowAtIndexPath: (NSIndexPath *) indexPath
      {
          static NSString *simple = @"CustomCellId";
  
          CustomCell *cell = (CustomCell *) [tableView dequeueReusableCellWithIdentifier:simple];
  
          if (cell == nil)
          {
              NSArray *nib =  [[NSBundle mainBundle] loadNibNamed:@"CustomCell" owner:self options:nil];
  
              for (id findCell in nib )
              {
                  if ( [findCell isKindOfClass: [CustomCell class]])
                  {
                      cell = findCell;
                  }    
              }
           }
           Person *managedObject = [self.someArray objectAtIndex: indexPath.row];
           cell.namelabel.text =  managedObject.displayName;
           return cell;
  }
  </code></pre>
  
  <p>The cell is hooked up in IB. I would want to detect when displayName changes, and update just the name label. 
  Thanks</p>