使用 swift 在 xcode 上显示错误消息后，显示警报一直让我退出

Question

我正在创建一个类似 Instagram 的应用程序，每当我关闭在缺少图像或文本时显示的显示警报时，它就会将我注销并重新登录。我怎样才能做到这一点，以便当我点击“好的”，只有显示警报消失并且不会让我退出？ 这是我的图片发布视图控制代码：

import UIKit
import Parse
import Foundation
class PostViewControllerPage1: UIViewController, UINavigationControllerDelegate, UIImagePickerControllerDelegate {
    func displayAlert(title:String, error:String) {
        var alert = UIAlertController(title: title, message: error, preferredStyle: UIAlertControllerStyle.Alert)
        alert.addAction(UIAlertAction(title: "OK", style: .Default, handler: { action in
            self.dismissViewControllerAnimated(true, completion: nil)
        }))
        self.presentViewController(alert, animated: true, completion: nil)
    }
    var photoSelected:Bool = false
    @IBOutlet weak var imageToPost: UIImageView!
    @IBAction func chooseImage(sender: AnyObject) {
        var image = UIImagePickerController()
        image.delegate = self
        image.sourceType = UIImagePickerControllerSourceType.PhotoLibrary
        image.allowsEditing = false
        self.presentViewController(image, animated: true, completion: nil)
    }
    func imagePickerController(picker: UIImagePickerController, didFinishPickingImage image: UIImage!, editingInfo: [NSObject : AnyObject]!) {
        println("Image selected")
        self.dismissViewControllerAnimated(true, completion: nil)
        imageToPost.image = image
        photoSelected = true
    }
    @IBOutlet weak var imageDescription: UITextField!
    @IBAction func postImage(sender: AnyObject) {
        var error = ""
        if (photoSelected == false) {
            error = "Please select an image to post"
        } else if (imageDescription.text == "") {
            error = "Please enter a message"
        }
        if (error != "") {
            displayAlert("Cannot Post Image", error: error)
        }
        else {
            var post = PFObject(className: "Post")
            post["Title"] = imageDescription.text
            post.saveInBackgroundWithBlock{(success: Bool, error: NSError?) -> Void in
                if success == false {
                    self.displayAlert("Could Not Post Image", error: "Please try again later")
                } else {
                    let imageData = UIImagePNGRepresentation(self.imageToPost.image)
                    let imageFile = PFFile(name: "image.png", data: imageData)
                    post["imageFile"] = imageFile
                    post.saveInBackgroundWithBlock{(success: Bool, error: NSError?) -> Void in
                        if success == false {
                            self.displayAlert("Could Not Post Image", error: "Please try again later")
                        } else {
                            println("posted successfully")
                        }
                    }
                }
            }
        }
    }
    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.
    }
}

我做错了什么？ 这是我的登录代码，因为我觉得这可能是问题的一部分：

import Foundation
import Parse
import UIKit
import Bolts
class LoginViewController: UIViewController, UITextFieldDelegate {      

    @IBOutlet weak var loginStatusLabel: UILabel!        
    @IBOutlet weak var emailTextField: UITextField!        
    @IBOutlet weak var passwordTextField: UITextField!
    @IBOutlet weak var loginButton: UIButton!


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

        emailTextField.delegate = self
        passwordTextField.delegate = self
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    @IBAction func loginButtonPress(sender: AnyObject) {

        login(emailTextField.text, password: passwordTextField.text)
    }

    func login(email: String, password: String)
    {

        PFUser.logInWithUsernameInBackground(email, password: password)
            {
            (user: PFUser?, error: NSError?) -> Void in
                if user != nil
                {
                    user!.fetchInBackground()
                    if user!.objectForKey("emailVerified") as! Bool
                    {
                        self.loginStatusLabel.text = "Success!"
                        println("successfulLogin")
                       self.performSegueWithIdentifier("login", sender: self)  
                    }
                    else if !(user!.objectForKey("emailVerified") as! Bool)
                    {
                        self.loginStatusLabel.text = "Verify your email address!"
                    }
                    else // status is "missing"
                    {
                        //TODO: Handle this error better
                        self.loginStatusLabel.text = "Verification status: Missing"
                    }
                }
                else
                {
                    if let errorField = error!.userInfo
                    {
                        self.loginStatusLabel.text = (errorField["error"] as! NSString) as String
                    }
                    else
                    {
                        // No userInfo dictionary present
                        // Help from http://stackoverflow.com/questions/25381338/nsobject-anyobject-does-not-have-a-member-named-subscript-error-in-xcode
                    }

                }
        }
    }

    override func viewDidAppear(animated: Bool) {
        if PFUser.currentUser() != nil {
            self.performSegueWithIdentifier("login", sender: self)
        }
    }

    func textFieldShouldReturn(textField: UITextField) -> Bool {
        textField.resignFirstResponder()
        return true;
    }

    override func viewWillAppear(animated: Bool) {
        self.navigationController?.navigationBarHidden = true
    }

    override func viewWillDisappear(animated: Bool) {
        self.navigationController?.navigationBarHidden = false
    }

}

Answer 1

alert.addAction(UIAlertAction(title: "OK", style: .Default, handler: { action in

        self.dismissViewControllerAnimated(true, completion: nil)

    }))

self.dismissViewControllerAnimated 在这一行中将关闭显示警报而不是警报本身的视图控制器。所以你所要做的就是注释或删除这行代码