如果导航堆栈中不存在视图控制器，则推送它

Posted 2023-03-22

【中文标题】如果导航堆栈中不存在视图控制器，则推送它

【英文标题】：Push a viewcontroller if it is not present in the navigation stack

【发布时间】：2018-05-02 09:28:56

【问题描述】：

我想检查导航堆栈中是否存在视图控制器。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。我已经尝试了以下代码。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)
      

【问题讨论】：

使用 if (aviewcontroller.isKind(of: TabProfileViewController.self)) 检查您的 aviewcontroller

【参考方案1】：

你在每个循环中检查它，所以如果第一个条件是真的，它可能会在下一次迭代中变为假，所以它会弹出并推送。试试下面的代码：

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)

【参考方案2】：

希望此代码对您有用。

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

【参考方案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)