Question

I have view controller A, table view controller B and view controller C. In A’s viewDidLoad method I add B as a subview of A. When an outlet in A is tapped then C is presented as a modal view. When an outlet is tapped in C; I need to call some method in B. How can I set B as C’s delegate if there is no direct relationship between the two? Is there another way to do this?

Answer 1

You may need to rethink your design. If “there is no direct relationship between B and C”, then C should not be calling methods on B. If C does need to call methods on B, then there is a relationship.

That said, since your view controller A knows about both of these objects, it can act as the link between them. You can have C call a method on A, which will then call a method on B. Of course, this requires C to have a reference to A; since you say that C is presented when a button is tapped in A, C has such a reference through its parentViewController property. For example:

// In C
- (IBAction) buttonPressed {
    [self.parentViewController passMessageToB:self];
}

// In A
- (void) passMessageToB: (id)sender {
    // sender is a reference to C, so B will be able to
    // pass information back if needed
    [B actOnMessageFromC:sender];
}

// In B
- (void) actOnMessageFromC: (id)sender {
    // Do whatever is needed
}

It’s possible to make this even more complex — you could even pass a particular selector to A that it could call on B, but at that point I think you would definitely need to reconsider your design and the connections between B and C.