How to navigate and pass data between UIViewControllers whose layout resembles a fork?

Question

I have a couple of UIViewControllers like shown

What I want is to pass data from B to C and also do that transition. So far I've come with 2 possible solutions:

1. Create a new instance of the C UIViewController class (and save a reference of the data in it), pop B from the navigation controller and push C into it.
2. Send the data to A, pop B from the navigation controller and then, in the viewWillAppear method of A, check if the data is not nil to know if it should send it to C and perform the segue .

Should I take any of those 2 approaches? Or is there a more elegant/proper solution for this situation?

Thanks

Answer 1

Organize data manager of parent controller or use Core Data.

In case of keeping data in parent controller, use dependency injection like described here

Here is an example for your case:

var dataFromC = "" // or nil
var dataFromB = "" // or nil

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "B",
        let viewController = segue.destinationViewController as? BViewController {
        viewController.dataFromC = self.dataFromC

//           declare method in BViewController
//           var method : ((String) -> ())? = nil
        viewController.method = {[weak self] valueFromB in
            self?.dataFromB = valueFromB
        }
    }

    if segue.identifier == "C",
        let viewController = segue.destinationViewController as? CViewController {
        viewController.dataFromB = self.dataFromB

//           declare method in CViewController
//           var method : ((String) -> ())? = nil
        viewController.method = {[weak self] valueFromC in
            self?.dataFromC = valueFromC
        }
    }
}

If you want to pass value to parent controller from BViewController , use self.method("yourValueFromB") where you will change the value. For case with CViewController use same approach.

Answer 2

As a general practice, B should send the data back to its originating view controller A with the help of delegate protocol pattern. A should be able to then decide in the delegate method implementation, what the data is received from B and where to send this data, which in this case is C.

This way your code looks more organised.