Button in custom cell in dynamic table: how to know which row in action method?

Question

I have a table of dynamic content. In the prototype cell I have a button. In that button's action method, how do I then determine which row's button was pressed?

(I know that, for example, in a segue method one can determine which row has been pressed by querying the selected path of the table view, but in this case, no row has actually been selected.)

Answer 1

There are of course ways of doing this using tags, or storing an indexPath in your cell etc.

I prefer to use something similar to the following, which I think is cleaner than the above. You could add this to a category UITableViewController.

- (NSIndexPath *)indexPathForCellSubview:(UIView *)subview
{
    if (subview) {
        UITableViewCell *cell = [self tableViewCellForCellSubview:subview];
        return [self.tableView indexPathForCell:cell];
    }
    return nil;
}

- (UITableViewCell *)tableViewCellForCellSubview:(UIView *)subview
{
    if (subview) {
        UIView *superView = subview.superview;
        while (true) {
            if (superView) {
                if ([superView isKindOfClass:[UITableViewCell class]]) {
                    return (UITableViewCell *)superView;
                }
                superView = [superView superview];
            } else {
                return nil;
            }
        }
    } else {
        return nil;
    }
}

Edit with suggestion from @staticVoidMan:

More concise implementation:

- (UITableViewCell *)tableViewCellForCellSubview:(UIView *)subview
{
    UIView *checkSuperview = subview.superview;

    while (checkSuperview) {
        if ([checkSuperview isKindOfClass:[UITableViewCell class]]) {
            break;
        } else {
            checkSuperview = checkSuperview.superview;
        }
    }
    return (UITableViewCell *)checkSuperview;
}

Answer 2

You could use tags, associated objects, or superview trickery.

Here's a question that has all three answers.

Tags

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *CellIdentifier = @"MySpecialCell";
    MySpecialCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (!cell) {
        cell = [[MySpecialCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
        cell.mySpecialTextView.delegate = self;
    }
    cell.mySpecialTextView.tag = indexPath.row;
    return cell;
}

- (void)textViewDidChange:(UITextView *)textView
    int rowOfTextViewThatJustChanged = textView.tag;
}

Associated Objects

static NSString *const kIndexPathKey = @"indexPathKey";

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *CellIdentifier = @"MultiSelectCell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (!cell) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
        UISwitch *switchView = [[UISwitch alloc] init];
        [switchView addTarget:self action:@selector(switchValueChanged:) forControlEvents:UIControlEventValueChanged];
        cell.accessoryView = switchView;
    }

    UISwitch *switchView = (id)cell.accessoryView;
    [self setIndexPath:indexPath onSwitch:switchView];
    switchView.on = [self isIndexPathSelected:indexPath];

    id item = [self itemAtIndexPath:indexPath];
    cell.textLabel.text = safePerformSelector(item, self.itemDescriptionSelector);
    return cell;
}

- (void)switchValueChanged:(UISwitch *)sender {
    NSIndexPath *indexPath = [self indexPathOfSwitch:sender];
    [self setRowSelected:sender.isOn atIndexPath:indexPath];
    [self.delegate didSelectItem:[self itemAtIndexPath:indexPath] atIndexPath:indexPath selected:sender.isOn sender:self];
}

- (void)setIndexPath:(NSIndexPath *)indexPath onSwitch:(UISwitch *)switchView {
    [switchView setAssociatedObject:indexPath forKey:kIndexPathKey];
}

- (NSIndexPath *)indexPathOfSwitch:(UISwitch *)switchView {
    return [switchView associatedObjectForKey:kIndexPathKey];
}


@implementation NSObject (AssociatedObjects)

- (void)setAssociatedObject:(id)object forKey:(NSString *const)key {
    objc_setAssociatedObject(self, (__bridge const void *)(key), object, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (id)associatedObjectForKey:(NSString *const)key {
    return objc_getAssociatedObject(self, (__bridge const void *)(key));
}

@end

Answer 3

Best approach:

-(void)buttonMethod:(UIButton *)sender event:(UIEvent *)event
{
    NSSet *touches = [event allTouches];
    UITouch *touch = [touches anyObject];
    CGPoint pointCurrent = [touch locationInView:self.tableView];
    NSIndexPath *indexPath = [self.tableView indexPathForItemAtPoint:pointCurrent];

    //...
}

---

PS: Provided you have done something like:

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

    [cell.someButton addTarget:self
                        action:@selector(buttonMethod:event:)
              forControlEvents:UIControlEventTouchUpInside];

    //...
}