Objective-C pass tableView indexPath to another method - ios

Question

I have this cellForRowAtIndexPath method here:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"Cell" forIndexPath:indexPath];
if (cell.accessoryView == nil) {
cell.accessoryView = [[Checkbox alloc] initWithFrame:CGRectMake(0, 0, 25, 43)];
cell.accessoryView.opaque = NO;
cell.backgroundColor = [UIColor clearColor];
[(Checkbox*)cell.accessoryView addTarget:self action:#selector(checkBoxTapped:forEvent:) forControlEvents:UIControlEventValueChanged];
}
NSString *sectionTitle = [contactSectionTitles objectAtIndex:indexPath.section];
NSArray *sectionContacts = [contactDirectoryFinal objectForKey:sectionTitle];
NSString *contacts = [[sectionContacts objectAtIndex:indexPath.row] valueForKey:#"item"];
cell.textLabel.text = contacts;
[(Checkbox*)cell.accessoryView setChecked: [[[sectionContacts objectAtIndex:indexPath.row] valueForKey:#"checkedItem"] boolValue] ];
return cell;
}
inside this method, I have this line:
[(Checkbox*)cell.accessoryView addTarget:self action:#selector(checkBoxTapped:forEvent:) forControlEvents:UIControlEventValueChanged];
which calls this method
- (IBAction)checkBoxTapped:(id)sender forEvent:(UIEvent*)event
{
}
What I am trying to do is adjust the way this method is called so I am also passing int the indexPath.row number
I got started with this:
[(Checkbox*)cell.accessoryView addTarget:self action:#selector(checkBoxTapped:forEvent:rowNumber:) forControlEvents:UIControlEventValueChanged];
and this
- (IBAction)checkBoxTapped:(id)sender forEvent:(UIEvent*)event rowNumber:(int)row
{
}
but I am new to selectors, my question is where do I pass in the rowNumber?

Answer 1

As you've found out you can't pass just any values with your selector, only the sender and the event. This is why you need another way pass the row number.
One method is to use the tag property on your control and retrieve it with [sender tag], however this approach will fail if the table indexes are changed without cellForRowAtIndexPath being called. It also won't work for sectioned table views.
A more robust approach is to use the location of your view to calculate the correct row. UITableView has a convenient method to do this:
- (IBAction)checkBoxTapped:(id)sender forEvent:(UIEvent*)event {
CGPoint checkBoxPosition = [sender convertPoint:CGPointZero toView:self.tableView];
NSIndexPath *indexPath = [self.tableView indexPathForRowAtPoint:checkBoxPosition];
}

Answer 2

As an alternative to passing it in ....
func checkBoxTapped(sender: CheckBox, withEvent event: UIEvent) {
if let tap = event.allTouches()?.first {
let location = tap.locationInView(tableView)
let indexPath = tableView.indexPathForRowAtPoint(location)
..... do something
}
}

Answer 3

*Update
As #Maddy 's comment
Do not use tag to represent the indexPath. It fails if the table view allows any rows to be moved, inserted, or deleted
this is not a good answer.*
As CheckBox is a UIView you can set its tag in cellForRowAtIndexPath: and then check for it in checkBoxTapped:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"Cell" forIndexPath:indexPath];
if (cell.accessoryView == nil) {
cell.accessoryView = [[Checkbox alloc] initWithFrame:CGRectMake(0, 0, 25, 43)];
cell.accessoryView.opaque = NO;
cell.backgroundColor = [UIColor clearColor];
[(Checkbox*)cell.accessoryView addTarget:self action:#selector(checkBoxTapped:forEvent:) forControlEvents:UIControlEventValueChanged];
}
NSString *sectionTitle = [contactSectionTitles objectAtIndex:indexPath.section];
NSArray *sectionContacts = [contactDirectoryFinal objectForKey:sectionTitle];
NSString *contacts = [[sectionContacts objectAtIndex:indexPath.row] valueForKey:#"item"];
cell.textLabel.text = contacts;
[(Checkbox*)cell.accessoryView setChecked: [[[sectionContacts objectAtIndex:indexPath.row] valueForKey:#"checkedItem"] boolValue] ];
// set the index to the tag.
cell.accessoryView.tag = indexPath.row
return cell;
}
- (IBAction)checkBoxTapped:(id)sender forEvent:(UIEvent*)event
{
// get the index from the tag value
NSInteger row = ((UIView *)sender).tag
}

Answer 4

You could use:
- (NSIndexPath *)indexPathForCell:(UITableViewCell *)cell
once you have the UITableViewCell object which can be accessed as sender.superview