通过 UITabBarController 让目标 VC 知道当前 VC 是委托的

Question

I'm trying to set the currentVC as the delegate for the destinationVC that is being navigated to through a UITabBarController and embedded in a UINavigationController .

I cant set the current VC as the delegate because prepareForSegue never gets triggered and the other solutions provided doesn't work either (bottom code).

This was all set up as Storyboards with Interface-builder

This is the architecture:

--> UITabBarController

-->UINavigationController

--> currentVC (Set this as the delegate)

-->UINavigationController

--> destinationVC

This does nothing:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

   print ("The Segue was triggered")
   let destinationVC = segue.destination as! MyViewController
   destinationVC.delegate = self

}

I also cant get this to work (it never goes through the IF statement):

override func viewDidLoad() {
        super.viewDidLoad()

        if let myDestinationVC = (self.tabBarController?.viewControllers![0] as? UINavigationController)?.viewControllers[0] as? destinationVC {
            print ("The IF statement was triggered")
            myDestinationVC.delegate = self
        }
}

I have a custom class for my TabBarController, that doesn't really do anything right now - I'm not sure if I need to reference that in the code above?

Answer 1

Here is a working and tested implementation. Not the best way to accomplish this, but will work for what you've described.

class MyTabBarViewController: UITabBarController, UITabBarControllerDelegate {

    // Replace with your sending view controller class's type
    var sendingViewController: SendingViewController?

    override func viewDidLoad() {
        super.viewDidLoad()
        self.delegate = self

        // Iterate all view controllers to make sure they are instantiated and
        // get reference to the sendingViewController
        viewControllers?.forEach {
            if let navigationController = $0 as? UINavigationController {
                // Replace with the type of your sending view controller
                if let sendingViewController = navigationController.topViewController as? SendingViewController {
                    self.sendingViewController = sendingViewController
                }
            }

        }
    }

    func tabBarController(_ tabBarController: UITabBarController, didSelect viewController: UIViewController) {

        if let navigationController = viewController as? UINavigationController {
            // Replace with the type of your receiving view controller
            if let receivingViewController = navigationController.topViewController as? ReceivingViewController,
                let sendingViewController = sendingViewController {
                // Perform actions here
                receivingViewController.view.backgroundColor = sendingViewController.view.backgroundColor
            }
        }
    }
}