Using delegate between sibling view controllers in containers

Question

I'm trying to make an app that uses three containers to show different content, but I'm having trouble communicating between the containers. I succeeded to use a segue to send some information at the tap of a button in one container to another container, but part of this information also has to be relayed to the third container. For this I wanted to use a delegate, but I cannot reference the right ViewController to the delegate variable.

So what I want goes as follows:

1. CollectionViewCell tapped, triggering segue to TableVC
2. TableVC receives information and updates the table
3. TableVC triggers delegate function in third VC
4. Third VC takes in some info and updates view

In the above I have managed to get 1 and 2 to work, but got stuck at 3.

I have made my protocol as follows:

protocol PurchaseDelegate {
    func addToTotalAmount(product : Product)
}

In the TableVC I have declared var delegate : PurchaseDelegate? = nil and in the IBAction triggered from the segue: delegate?.addToTotalAmount(product)

In the third VC I have implemented the delegate as follows:

class thirdVC:UIViewController,PurchaseDelegate {
    func addToTotalAmount(product : Product) {
        println("Adding....")
    }
}

All three containers are within a main VC that does some initial stuff in the application.

My problem is, that I don't know how to get a reference from thirdVC to my delegate variable in my tableVC.

Thanks in advance.

Answer 1

I ended up finding the solution to the problem after a bit further searching with inspiration from @Anna Dickinson.

Firstly, the containers must be ordered correctly in the storyboard. The container whose view controller implements the delegate protocol must be first in the list and then the other view controller further down.

Then, in the main view controller - the view controller for the view with the containers - the prepareForSegue function is implemented, since it will be triggered as the containers are initialized.

This all of the code remains as above, but the main view controller will be something like the following:

class MainViewController: UIViewController {
    var actionVC : FirstViewController! // This is the one, that implements the delegate protocol
    var tableVC : SecondViewController! // This is the one, that has a delegate variable
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        if(segue.identifier == "firstVC"){
            self.actionVC = segue.destinationViewController as FirstViewController
        } else if(segue.identifier == "secondVC"){
            self.tableVC = segue.destinationViewController as SecondViewController
            self.tableVC.delegate = self.actionVC
        }
    }
}

I'm not sure if the is the right, nor the best way to do this, but it works perfectly for what I need.