UITableView Cell - get IndexPath.row from button? - iphone

Question

I currently have a button defined in a cell and a method to track its UITouchDown action as shown:
- (void) clickedCallSign:(id)sender {
int index = [sender tag];
NSLog(#"event triggered %#",index);
}
- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath {
//Callsign button
UIButton *button;
CGRect rect = CGRectMake(TEXT_OFFSET_X, BORDER_WIDTH, LABEL_WIDTH, LABEL_HEIGHT);
button = [[UIButton alloc] initWithFrame:rect];
cell.tag=[indexPath row];
button.tag=[indexPath row];
[button addTarget:self action:#selector(clickedCallSign:) forControlEvents:UIControlEventTouchDown];
[button setBackgroundColor:[UIColor redColor]];
[button setTitle:#"hello" forState:UIControlStateNormal];
[cell.contentView addSubview:button];
[button release];
}
However when I click a cell in the simulator, the console debug message is: "event triggered (null)" and my app crashes shortly after.
How can I correctly get the indexPath.row value into my clickedCallSign method?

Answer 1

First off, index is an int, so your NSLog needs to look like this (note the %d):
NSLog(#"event triggered %d", index);
(It's possible that this leads to a crash, but it's also likely that something else entirely is going that causes the instability.)

Answer 2

Tag is good until you haven't both sections and rows. Try another way to get index path:
- (void)tableView:(UITableView*)tableView willDisplayCell:(UITableViewCell*)cell forRowAtIndexPath:(NSIndexPath*)indexPath {
//...
[button addTarget:self action:#selector(clickedCallSign:withEvent:) forControlEvents:UIControlEventTouchDown];
//...
}
// Get the index path of the cell, where the button was pressed
- (NSIndexPath*)indexPathForEvent:(id)event
{
NSSet *touches = [event allTouches];
UITouch *touch = [touches anyObject];
CGPoint currentTouchPosition = [touch locationInView:self.tableView];
return [self.tableView indexPathForRowAtPoint:currentTouchPosition];
}
- (IBAction)clickedCallSign:(id)sender withEvent:(UIEvent*)event
{
NSIndexPath* buttonIndexPath = [self indexPathForEvent:event];
}

Answer 3

If you don't want to use the tag field, have the button invoke this method:
- (void)tapAccessoryButton:(UIButton *)sender
{
UIView *parentView = sender.superview;
// the loop should take care of any changes in the view heirarchy, whether from
// changes we make or apple makes.
while (![parentView.class isSubclassOfClass:UITableViewCell.class])
parentView = parentView.superview;
if ([parentView.class isSubclassOfClass:UITableViewCell.class]) {
UITableViewCell *cell = (UITableViewCell *) parentView;
NSIndexPath *indexPath = [self.tableView indexPathForCell:cell];
[self tableView:self.tableView accessoryButtonTappedForRowWithIndexPath:indexPath];
}
}