让目标VC知道当前VC是通过UITabBarController委托的。

Question

我正在尝试将currentVC设置为通过UINavigationController.导航到的destinationVC的委托

我不能将当前的VC设置为委托，因为prepareForSegue永远不会被触发，而且提供的其他解决方案也不能工作(下面的代码)。

这一切都被设置为Interface-builder的故事板

这是一个体系结构：

-> UITabBarController

-> currentVC (设置为委托)->UINavigationController

-> destinationVC

这没什么用：

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

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

}

我也不能让它起作用(它从来不通过IF语句)：

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
        }
}

我为我的TabBarController提供了一个自定义类，它现在什么也不做--我不确定是否需要在上面的代码中引用它？

Answer 1

下面是一个工作和测试的实现。这不是实现这一目标的最佳方法，但你所描述的一切都会奏效。

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
            }
        }
    }
}