Implementing a basic callback in Objective C

How does one implement a raw callback in objective C?

I just want to notify a ViewController wh开发者_StackOverflow中文版en one of my UITableViewCell objects(custom cell) detects touch.

I need to notify my RootViewController so that it can create an object of another ViewController and push it on the navigation stack.

You can use a custom init method like below for secondVC and store the _sender in global or class variable. like

id sender;

- (id)initWithSender:(id)_sender
{
    self = [super init];
    if (self) {
        sender=_sender;
    }
    return self;
}

from RootVC initialize secondvc as follows and define a method named -(void) touchDetected; in rootvc.

    secondvc=[[SecondVC alloc] initWithSender:self];
    [[self navigationController] pushViewController: secondvc animated:YES];    

when the touch is detected in secondvc call, this will notify your rootvc that the touch is detected in secondvc.

[sender touchDetected];

You can probably override the Table view delegate method didSelectRowAtIndex: to detect the touch.Then u can push the view controller using pushViewController: method of Navigation controller

If the cell object you are referring is a button then you can do by [button addTarget:self action:@selector(methodYouWantToInvoke)];

You need to set your ViewController to be the delegate of your table view, then implement the tableView:didSelectRowAtIndexPath: method. This is sample code directly from Apple.

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
 {
     [tableView deselectRowAtIndexPath:indexPath animated:NO];
     BATTrailsViewController *trailsController = [[BATTrailsViewController alloc] initWithStyle:UITableViewStylePlain];
     trailsController.selectedRegion = [regions objectAtIndex:indexPath.row];
     [[self navigationController] pushViewController:trailsController animated:YES];
     [trailsController release];
}