弹出ViewController后，如何检查，堆栈顶部的ViewController是特定的？

Question

假设我目前在BaseViewController上。我可以从另外2个视图控制器（例如A和B）中访问该视图控制器类。因此，当我弹出BaseViewController时，如何检查堆栈顶部是否存在A或B？这是我的下面代码（在BaseViewController内部）：

func goToAOrBViewController {
   // If after popping viewController is A do this
   navigationController.popViewController(animated: true)
   // Id after popping viewController is B do this
   // Instantiate B and push it
}

Answer 1

有很多方法可以做到这一点

最简单的方法

    func visibleViewController() -> UIViewController? {
        let appDelegate = UIApplication.shared.delegate
        if let window = appDelegate!.window {
            return window?.visibleViewController
        }
        return nil
    }

    func goToAOrBViewController {
       // If after popping viewController is A do this
       navigationController.popViewController(animated: true)
       if visibleViewController() == viewControllerA{
           //Do stuff for A
       }else{
           //Do stuff for B
       }
    }

第二种明显的方法

    let topController = UIApplication.sharedApplication().keyWindow?.rootViewController
    if topController == viewControllerA {
        //Do stuff for A
    }else{
        //Do stuff for B
    }

Answer 2

您可以同时弹出并推送视图控制器。

未测试：

navigationController?.viewControllers.removeLast()
let topVC = navigationController?.viewControllers.last

if topVC == A {
  navigationController?.viewControllers.append(A)
  navigationController?.setViewControllers(A, animated: false)
} else {
  navigationController?.viewControllers.append(B)
  navigationController?.setViewControllers(B, animated: false)
}

Answer 3

内部BaseViewController类：

func goToAOrBViewController() {
   guard let navigationController = self.navigationController else { return }
   navigationController.popViewController(animated: false)
   guard let viewController = navigationController.topViewController else { return }
   if viewController is ViewControllerA {
      // Do something for A
   } else if viewController is ViewControllerB {
      // Do Something for B
   }
   // You need not put else-if case if you are sure BaseVC is reachable from A and B only (just use else)
}