Swift 按下 UIButton 后 UILabel 以编程方式更新

Question

我正在寻找一个 UILabel 程序来确认注册是否成功。我迷失了如何去创造它。我在 SignUpViewController 中放置了一个标签。不过，我不知道该去哪里设置代码来提供反馈。请让我知道如何去做。提前谢谢你。

import UIKit

class signUpViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate, UITextFieldDelegate {

    @IBOutlet var usernameTextfield: UITextField!

    @IBOutlet var emailTextfield: UITextField!

    @IBOutlet var passwordTextfield: UITextField!

    @IBOutlet var compasswordTextfield: UITextField!

    @IBOutlet var birthdateTextfield: UITextField!

    @IBOutlet var combirthdateTextfield: UITextField!

    @IBOutlet var confirmationLable: UILabel!

    @IBAction func signupButton(sender: AnyObject) {

        var pahser:PFUser = PFUser()
        pahser.username = usernameTextfield.text
        pahser.email = emailTextfield.text
        pahser.password = passwordTextfield.text

        pahser.signUpInBackgroundWithBlock{
            (success:Bool!, error:NSError!)->Void in
            if error == nil {
                println("Signup Successfull")

                var imagePicker:UIImagePickerController = UIImagePickerController()
                imagePicker.sourceType = UIImagePickerControllerSourceType.PhotoLibrary

                imagePicker.delegate = self

                self.presentViewController(imagePicker, animated: true, completion: nil)

            }else{

                let errorString = error.localizedDescription
                println(errorString)

            }
        }
    }


    func imagePickerController(picker: UIImagePickerController!, didFinishPickingMediaWithInfo info: NSDictionary!) {
        let pickedImage:UIImage = info.objectForKey(UIImagePickerControllerOriginalImage) as UIImage
        let scaledImage = self.scaleImageWith(pickedImage, and: CGSizeMake(100, 100))
        let imageData = UIImagePNGRepresentation(scaledImage)
        let imageFile:PFFile = PFFile(data: imageData)
        PFUser.currentUser().setObject(imageFile, forKey: "profileImage")
        PFUser.currentUser().saveInBackground()

        picker.dismissViewControllerAnimated(true, completion: nil)

    }

    func scaleImageWith(newImage:UIImage, and newSize:CGSize)->UIImage{
        UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0)
        newImage.drawInRect(CGRectMake(0, 0, newSize.width, newSize.height))
        UIGraphicsEndImageContext()

        return newImage
    }



    override func viewDidLoad() {
        super.viewDidLoad()
        self.passwordTextfield.delegate = self;
        self.usernameTextfield.delegate = self;
        self.emailTextfield.delegate = self;
        self.compasswordTextfield.delegate = self;
        self.birthdateTextfield.delegate = self;
        self.combirthdateTextfield.delegate = self

    }
        // Do any additional setup after loading the view.


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

    func textFieldShouldReturn(textField: UITextField!) -> Bool {
        self.view.endEditing(true);
        return false;
    }

    /*
    // MARK: - Navigation

    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        // Get the new view controller using segue.destinationViewController.
        // Pass the selected object to the new view controller.
    }
    */

}

Answer 1

pahser.signUpInBackgroundWithBlock{
    (success:Bool!, error:NSError!)->Void in
        if error == nil {
            println("Signup Successfull")
            confirmationLable.text = "Signup Successfull"
            var imagePicker:UIImagePickerController = UIImagePickerController()
            imagePicker.sourceType = UIImagePickerControllerSourceType.PhotoLibrary

            imagePicker.delegate = self
            dispatch_async(dispatch_get_main_queue()) {
                self.presentViewController(imagePicker, animated: true, completion: nil)
            }


        }else{

            let errorString = error.localizedDescription
            confirmationLable.text = error.localizedDescription
            println(errorString)

        }
    }

希望这对您有所帮助..:)

Answer 2

pahser.signUpInBackgroundWithBlock{ 在注册 api 调用 returns 时调用完成块，无论是失败还是成功。您可以在该块内设置标签值。
此外 UI 更新需要在主队列中完成。
如果你想延迟 presentViewController，你可以查看 arthankamal 的答案函数调用。
但通常情况下最好仅在出现故障时指示用户。

pahser.signUpInBackgroundWithBlock{
    (success:Bool!, error:NSError!)->Void in
     if (error == nil)
     {
         dispatch_async(dispatch_get_main_queue(),  {
           confirmationLable.text = "Success"
        });

     }
     else 
     {
        dispatch_async(dispatch_get_main_queue(),  {
           confirmationLable.text = "Failure"
        });
     }
}

Answer 3

解决方案 1： 在块内延迟 presentViewController 函数，检查此 link 如何延迟，dispatch_after - GCD in swift?

pahser.signUpInBackgroundWithBlock{
        (success:Bool!, error:NSError!)->Void in
        if error == nil {

            confirmationLable.text = "Sign Up Success";

            // Delay the Presenting View Controller, 
            // so that you can see that your sign up label success message
            delay(0.4) {
                self.presentViewController(imagePicker, animated: true, completion: nil)
            }
        }else{
            let errorString = error.localizedDescription
            println(errorString)
        }
    }

// Function To delay your present view controller, from Whosebug answer
func delay(delay:Double, closure:()->()) {
dispatch_after(
    dispatch_time(
        DISPATCH_TIME_NOW,
        Int64(delay * Double(NSEC_PER_SEC))
    ),
    dispatch_get_main_queue(), closure)
}

解决方案 2： 使用 Toast View，检查这个 github 项目 https://github.com/Rannie/Toast-Swift

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