ios - swift4 : how to check if user logged befor tab bar item clicked

Question

这个问题以前有人问过，也有人回答过，我的问题不是唯一的，但一定有什么遗漏。我只是想检查用户之前是否登录过应用程序，因为他的数据存储在 UserDefaults 中，但这对我不起作用，这是我的 TabBarViewController 类

class TabViewController: UITabBarController, UITabBarControllerDelegate {
override func viewDidLoad() {
    super.viewDidLoad()

    self.delegate = self
}
// UITabBarDelegate
override func tabBar(_ tabBar: UITabBar, didSelect item: UITabBarItem) {
    print("Selected item")
}

// UITabBarControllerDelegate
func tabBarController(_ tabBarController: UITabBarController, didSelect viewController: UIViewController) {
    if(viewController is MessagesViewController) {
        print("trueee")
        if(UserStorage.id == "") {
           Toast.toast(messsage: "not loggoed user", view: self.view)
        } 
    } else {
        print("faaaaaaaalse")
    }
    print("Selected view controller")
}
}

我想检查用户是否打开 MessageViewController 然后如果用户登录打印一些东西但它总是打印 faaaaaaaalse

note: Toast.toast() is a function i created to show toast and UserStorage.id returns user id stored in USerDefaults

这是显示我的结构的图像: 我该怎么办？

Answer 1

只是你的标签栏的根 Controller 是 2 个导航 Controller ，而不是 MessageViewController。首先，对于 tabBarController，您必须找到包含 MessageViewController 的 navigationController，而不是在此导航中找到所需的 ViewController。

所以我有适合您的解决方案:

import UIKit

class TabbarController: UITabBarController, UITabBarControllerDelegate {

override func viewDidLoad() {
    super.viewDidLoad()
    self.delegate = self
    // for tab bar initialization
    if let viewControllers  = self.viewControllers,
        viewControllers.count >= 1,
        // the index of viewController is 0 here, but if your tab bar's started controller is not 0 you can set yours
        let navigationController = viewControllers[0] as? UINavigationController {
        for controller in navigationController.viewControllers {
            if let messagesViewController = controller as? MessagesViewController {
                doWithMessagesViewControllerWhatYouWant(_viewController: messagesViewController)
            }
        }
    }
}

// UITabBarControllerDelegate
func tabBarController(_ tabBarController: UITabBarController, didSelect viewController: UIViewController) {
    if let navigationController = viewController as? UINavigationController{
        for controller in navigationController.viewControllers {
            if let messagesViewController = controller as? MessagesViewController {
                doWithMessagesViewControllerWhatYouWant(_viewController: messagesViewController)
            }
        }
    }
}

private func doWithMessagesViewControllerWhatYouWant(_viewController: MessagesViewController) {
    print("do some operations with messagesViewController")
    if(UserStorage.id == "") {
       Toast.toast(messsage: "not loggoed user", view: self.view)
    } 
}

}