认为没有跑

Question

我正在使用if语句来运行segue。我有if语句在成功运行时打印一条消息。但是，segue没有运行，我不知道为什么。

override func viewDidLoad() {
    super.viewDidLoad()

    firstField.delegate = self
    signUpButtonOutlet.isEnabled = false
    // Do any additional setup after loading the view.

    let fetchRequest: NSFetchRequest<Check> = Check.fetchRequest()

    do {
        //go get the results
        let searchResults = try getContext().fetch(fetchRequest)

        //I like to check the size of the returned results!
        print ("num of results = \(searchResults.count)")

        //You need to convert to NSManagedObject to use 'for' loops
        for check in searchResults as [NSManagedObject] {
            //get the Key Value pairs (although there may be a better way to do that...
            print("the value was\(check.value(forKey: "isLoggedIn"))")

            if (check.value(forKey: "isLoggedIn") != nil) {
                self.performSegue(withIdentifier: "loggedInTrue", sender: self)
                print("if statement ran")
            } 


        }


    } catch {
        print("Error with request: \(error)")
    }

}

Answer 1

将登录状态存储在viewDidLoad中，并在viewDidAppear中执行搜索。如果登录状态为true，则会隐藏第一个ViewController。

override func viewWillAppear(_ animated: Bool) {
    if (isloggedIn != false) {
        self.view.isHidden = true
    } else {
        self.view.isHidden = false
    }
}

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(true)
    if (isloggedIn != false) {
        self.performSegue(withIdentifier: "loggedInTrue", sender: self)
    }
}

或

dispatch_async(dispatch_get_main_queue()) {
   self.performSegueWithIdentifier("loggedInTrue", sender: self)
}

Answer 2

最好的办法是在检查用户是否已登录后，从appDelegate加载“loggedIn”控制器。

因此，例如在app委托的didFinishLaunchingWithOptions方法中检查用户默认情况，以查看用户是否登录

if UserDefaults.standard().bool(forKey: "logged_in") == true {

    self.window = UIWindow(frame: UIScreen.main.bounds)
    let storyboard = UIStoryboard(name: "YOURSTORYBOARDNAME", bundle: nil)
    let loggedIn = storyboard.instantiateViewController(withIdentifier: "LOGGEDIN") as! UIViewController
    self.window?.rootViewController = loggedIn
}

显然，要使用此功能，您需要在用户实际登录时将loggedIn变量设置为true。就像这样

UserDefaults.standard().setBool(true, forKey: "logged_in")

您必须注意的一件事是，将YOURSTORYBOARDNAME更改为您的实际故事板，您还必须在故事板中设置该控制器的标识符