what is the maximum limitation of view tag on an UITableViewCell

Question

I put a DragView (subclass of UIView) on a UITableViewCell with tag (row+20000)

- (UITableViewCell *)tableView:(UITableView *)tableView 
     cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{   

   NSInteger row=[indexPath row];
   NSInteger section=[indexPath section];
   static NSString *SimpleTableIdentifier1 = @"CellTableIdentifier";
   UITableViewCell *cell=[tableView dequeueReusableCellWithIdentifier: SimpleTableIdentifier1 ];
   if  (cell == nil) {
      cell=[[[UITableViewCell alloc] initWithFrame:CGRectZero 
      CGRect dragRect =CGRectMake(12.0f,6.0f,24.0f,24.0f);
      DragView *dragger =[[DragView alloc]  initWithFrame:dragRect];
      [dragger setTag: row+20000 ];

   }
   DragView *newDragger=(DragView*)[cell viewWithTag: row+20000 ];//error

   //......
   return cell;
}

But when I try to use the codes (line marks with 'error') to access the DragView, debugger shows that newDragger returns 0x0 which means no object.

I do not know where is wrong. I just guess there may be the reason of the amount limitation of maximium tag )

Welcome any comment.

Thanks

interdev

Answer 1

tag property has NSInteger type and can have any value NSInteger can hold, so 20000 should not cause problems.

Code you posted definitely lacks some details - do you actually put dragger into your cell? Note also that it is recommended not to add subviews to UITableViewCell directly - you must add them to cell's contentView instead:

[cell.contentView addSubView: dragger];

and access it later:

DragView *newDragger=(DragView*)[cell.contentView viewWithTag: row+20000 ];

Also note that your code will not work when table reuses the cells, that is when cell is used for a row different from the row it was initially created for and you will try to access subview with wrong tag anyway.

P.S. Also see this question Detecting which UIButton was pressed in a UITableView. It deals with buttons but may be it will be helpful for your custom view as well.

Answer 2

The cell may be come from dequeueReusableCellWithIdentifier: method, and this cell's previous row number may be someone else. So, the tag cannot be trusted.