Question

So lately I have been trying ways to pass data from a child to a parent view controller. I have settled with two. The delegates approach:

http://timneill.net/2010/11/modal-view-controller-example-part-2/

and the simple approach of just passing reference of the parent view controller to the child view controller before the child controller is pushed (UINavigationController) or presented (via modal presentation)

- (IBAction)myAction:(id)sender{
    MyViewController *myView = 
        [[MyViewController alloc] init];

    myView.isLinking = YES;
    myView.parent = self;


    // present child pushing or presentation logic here

    [sender resignFirstResponder];
}

but I’m wondering why should I go with delegates if I can do the latter when I only just want to be able to pass data from child to parent view controllers?

Also, there’s only about a few answers on SO where doing the latter is recommended. In fact, I can’t remember if there are.

So I was wondering, why is doing the latter not recommended and why are there more people suggesting delegates or even retrieving the controller from the application delegate?

Answer 1

Because the second approach ties both the parent to the child and vice versa, making a circular dependency. This is bad OOP. Using delegates means the child view can be used from any manner of calling code, now or in the future.