推送到另一个ViewController

Question

我有推送到另一个视图控制器的问题。我创建了一个简单的登录系统但问题是，即使密码错误，它也会将我推送到默认的视图控制器。

import UIKit
import Parse

class ViewController: UIViewController {

@IBOutlet weak var usernameTextField: UITextField!
@IBOutlet weak var passwordTextField: UITextField!

func createAlert(title: String, message: String) {

    let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)

    alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { (alert) in

    }))
    self.present(alert, animated: true, completion: nil)

}

@IBAction func loginButton(_ sender: Any) {

    // ************ Login Page ************

    // Username error checking

    if usernameTextField.text == "" {

        let usernameAlert = UIAlertController(title: "Username is missing", message: "Please enter your username", preferredStyle: UIAlertControllerStyle.alert)

        usernameAlert.addAction(UIAlertAction(title: "OK", style: .default, handler: { (action) in
            }))
        self.present(usernameAlert, animated: true, completion: nil)

        // Password error checking

    } else {

        if passwordTextField.text == "" {

            let passwordAlert = UIAlertController(title: "Passwors is missing", message: "Please enter your password", preferredStyle: UIAlertControllerStyle.alert)

            passwordAlert.addAction(UIAlertAction(title: "OK", style: .default, handler: { (action) in
                self.dismiss(animated: true, completion: nil)
            }))
            self.present(passwordAlert, animated: true, completion: nil)            }

        else {

        PFUser.logInWithUsername(inBackground: usernameTextField.text!, password: passwordTextField.text!, block: { (user, error) in

            if error != nil {



                var displayErrorMessage = "Please try again later."

                if let errorMessage = error as NSError? {

                    displayErrorMessage = errorMessage.userInfo["error"] as! String

                }


                self.createAlert(title: "Login Error", message: displayErrorMessage)
            } else {

                print ("Logged in")

                let storyBoard = UIStoryboard(name: "Main", bundle: nil)

                let cameraVC = storyBoard.instantiateViewController(withIdentifier: "CameraViewController") as! CameraViewController

                self.navigationController?.pushViewController(cameraVC, animated: true)

            }
            })
        }
    }

}
override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.



        }

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}
}

注意：当用户名和密码有效时，我在调试区域中显示“登录”消息。

Answer 1

你是否在直接按钮中给出了segue连接，例如

  

因此如果单击按钮直接转到另一个VC，它就不会检查条件。

如果您使用的是故事板ID，则删除VC之间的连接，您可以直接访问

 let storyBoard = UIStoryboard(name: "Main", bundle: nil)

            let cameraVC = storyBoard.instantiateViewController(withIdentifier: "CameraViewController") as! CameraViewController

            self.navigationController?.pushViewController(cameraVC, animated: true)

否则

  

使用direclty类

的面向连接的segue

 [self performSegueWithIdentifier:@"identifierName" sender:self];

像

一样打电话

else {

            print ("Logged in")
            performSegue(withIdentifier: "identifierName", sender: self)

            }

Answer 2

如果你使用segue会更好。首先使用标识符为CameraViewController创建一个segue。然后，在编码中调用它。

performSegue（withIdentifier：“mySegueID”，sender：self）

Answer 3

1）从故事板中简单地从IBAction目标中删除您的代码。

2）在故事板中选择你的segue - ＆gt;属性 - ＆gt;标识符 - ＆gt;在这里设置一个标识符

3）在您的代码中添加此委托。

  override func shouldPerformSegue(withIdentifier identifier: String, sender: Any?) -> Bool {
        if  identifier == "youridentifier" {
            if username and password correct
            {
                return true
            }
            else
            {
                show alert here
                return 
            }
        }
        return true
    }

简单！