Question

我想检查一个视图控制器是否存在于导航堆栈中。如果它存在，我需要弹出它，否则我需要将其推送到导航堆栈。我试过以下代码。如果它不存在，则控制正在转移到else块但我无法导航到屏幕。请帮帮我

 for aViewController in viewControllers! {

    if aViewController is TabProfileViewController {

      self.navigationController?.popToViewController(aViewController, animated: true)

     }

    else {

        let lvc = self.storyboard?.instantiateViewController(withIdentifier: "LoginViewController") as? LoginViewController
        self.navigationController?.pushViewController(lvc!, animated: true)
      }
}

Answer 1

你在每个循环中检查它，所以如果第一个条件为真一次可能在下一次迭代中变为假，那么它将弹出并推送。尝试以下代码：

if let viewController = viewControllers?.first(where: { $0 is TabProfileViewController }) {
    navigationController?.popToViewController(viewController, animated: true)
} else {
    let lvc = storyboard?.instantiateViewController(withIdentifier: "LoginViewController") as? LoginViewController
    navigationController?.pushViewController(lvc!, animated: true)
}

Answer 2

希望此代码适合您。

    if navigationController != nil && !(navigationController?.topViewController is YOURCONTROLLER) {
        for aViewController in (navigationController?.viewControllers)! 
          {
            if aViewController is YOURCONTROLLER {
            //Your controller found
            }else{
               //push using navigation
            }
        }
    }

Answer 3

这是另一种方法：

 if arrViewController != nil && !(arrViewController?.topViewController is TabProfileViewController) {
        for aViewController in (arrViewController?.viewControllers)! {
            if aViewController is Dashboard {
                _ = self.navigationController?.popToViewController(aViewController, animated: true)
                break
            }
        }
    }else{
         let lvc = self.storyboard?.instantiateViewController(withIdentifier: "LoginViewController") as? LoginViewController
         self.navigationController?.pushViewController(lvc!, animated: true)
    }

如果视图控制器不在导航堆栈中，请将其推送

3 个答案: