如果导航堆栈中不存在，则推送 viewcontroller

Question

我想检查导航堆栈中是否存在 viewcontroller。如果它存在，我需要弹出它，否则我需要将它推送到导航堆栈。我尝试了以下代码。如果它不存在，控制权将转移到 else 块，但我无法导航到屏幕。请帮助我

 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一次为真，它可能在下一次迭代中变为假，所以它会弹出和推送。试试下面的代码：

if let viewController = viewControllers?.first(where: { [=10=] is TabProfileViewController }) {
    navigationController?.popToViewController(viewController, animated: true)
} else {
    let lvc = storyboard?.instantiateViewController(withIdentifier: "LoginViewController") as? LoginViewController
    navigationController?.pushViewController(lvc!, animated: true)
}

Answer 2

希望这段代码对你有用。

    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)
    }

如果导航堆栈中不存在，则推送 viewcontroller

Push a viewcontroller if it is not present in the navigation stack

swift

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pushviewcontroller