swift - performSegueWithIdentifier 导致崩溃

Question

我正在 XCode 6 上使用框架 PARSE 设置注册/登录页面。

当我尝试执行一个 segue(它拼写正确)时，悬停，应用程序崩溃，即使 segue 在 if 语句中也是如此。

代码如下:

import UIKit
import Parse

class ViewController: UIViewController, UINavigationControllerDelegate{

   var signUpMode = false

   func displayAlert(title:String, message:String){        
       let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.Alert)
       alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))
       self.presentViewController(alert, animated: true, completion: nil)        
   }

   //Outlet and actions    

   @IBOutlet var username: customTextField!    
   @IBOutlet var email: customTextField!  
   @IBOutlet var password: customTextField!

   //Need the outlets for changes betweeen signUp and logIn modes!!!


   @IBAction func signUp(sender: AnyObject) {

      if signUpMode == true {

         var user = PFUser()
         user.username = username.text
         user.password = password.text
         user.email = email.text

         // other fields can be set just like with PFObject
         //user["phone"] = "415-392-0202"

         user.signUpInBackgroundWithBlock {
            (succeeded: Bool!, error: NSError!) -> Void in
            if error == nil {
                // Hooray! Let them use the app now.
            } else {
                println("error")
                self.displayAlert("Username already in use", message: "Please use another username")
            }
         }
      }
      else {

         PFUser.logInWithUsernameInBackground(email.text, password:password.text) {
            (user: PFUser!, error: NSError!) -> Void in

            if user != nil {                    
                self.displayAlert("You're in", message: "And you'll be successful")                    
                self.performSegueWithIdentifier("goToPost", sender: self)                    
            } else {                    
                self.displayAlert("Wrong username or password", message: "Please try again")
            }
        }
   }    


  override func viewDidLoad() {
    super.viewDidLoad()    
  }

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


  override func viewWillAppear(animated: Bool) {

      if signUpMode == false {            
          self.username.hidden = true
          self.email.placeholder = "username"           
      }        
  }

  override func viewDidAppear(animated: Bool) {

      if PFUser.currentUser() != nil {            
          performSegueWithIdentifier("goToPost", sender: self)            
      }      
  }
}

segue 在 viewWillAppear 方法中。PFUser().currentUser() 存储有关当前登录用户的信息，因此如果没有用户登录，则为 nil。

你能找出它崩溃的原因吗？我试图将 segue 放在 viewDidLoad 中，但没有别的，它甚至没有崩溃。

Answer 1

尝试在 viewDidAppear: 中进行 segueing:并检查您的 segue 标识符是否与 Storyboard上的标识符匹配。