Xcode 7 + swift。 「在聲明之前使用局部變量'_'錯誤

Question

嘗試創建函數來檢查用戶輸入和存儲數據時，出現上述錯誤。我的項目建立良好，直到我達到這個功能RegisterButtonTapped()。有沒有人有一些結構或語法的變化，可以擺脫這個錯誤？

@IBAction func RegisterButtonTapped(sender: AnyObject) { 

    let userEmail = userEmailTextField.text; 
    let userPassword = userEmailTextField.text; 
    let userRepeatPassword = userRepeatPasswordTextField.text; 


    // Check for empty fields 
    if(userEmail!.isEmpty || userPassword!.isEmpty || userRepeatPassword!.isEmpty){ 

     displayAlertMessage("All fields are required"); 

     return; 
    } 

    // Check if passwords match 
    if(userPassword != userRepeatPassword){ 

     displayAlertMessage("Passwords do not match"); 

     return; 
    } 

    // Store Data 
    NSUserDefaults.standardUserDefaults().setObject(userEmail, forKey: "userEmail"); 
    NSUserDefaults.standardUserDefaults().setObject(userEmail, forKey: "userPassword"); 
    NSUserDefaults.standardUserDefaults().synchronize(); 

    // Display Alert message with confirmation 
    var myAlert = UIAlertController(title:"Alert",message:"Registration is successful, thank you.",preferredStyle: UIAlertControllerStyle.Alert); 

    func displayAlertMessage(userMessage:String){ 

     var myAlert = UIAlertController(title:"Alert",message: userMessage, preferredStyle: UIAlertControllerStyle.Alert); 

     let okAction = UIAlertAction(title:"ok",style: UIAlertActionStyle.Default, handler:nil); 

     myAlert.addAction(okAction); 
     self.presentViewController(myAlert, animated: true, completion: nil); 
    } // END OF FUNCTION 'displayAlertMessage()' 



} // END of FUNCTION 'RegisterButtonTapped()' 

Answer 1

您已經聲明displayAlertMessage您呼叫後，將它的聲明附近RegisterButtonTapped（）如果你想保持它作爲一個嵌套函數的頂部，否則將其移出RegisterButtonTapped的（）。

除此之外，您有兩個變量，都稱爲myAlert，第一個變量沒用，並且您將userEmail保存爲電子郵件和密碼，並且不需要調用synchronize（）。

Answer 2

有一些細節讓它正確運行。 displayAlertMessage在調用之後被聲明在註冊函數中，並且我們得到警告。當您獲得成功時，您必須使用成功消息調用該函數，並且不要在警報函數內聲明var myAlert。最後的細節：當獲取UITextFields值時，您會收到電子郵件輸入字段並將其設置爲密碼值，因此驗證將是錯誤的。

下面的代碼示例是偉大工程：

class ViewController: UIViewController { 

    @IBOutlet var userEmailTextField:UITextField! 
    @IBOutlet var userPassTextField:UITextField! 
    @IBOutlet var userRepeatPasswordTextField:UITextField! 

    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. 
    } 

    @IBAction func RegisterButtonTapped(sender:UIButton) { 
     let userEmail = userEmailTextField.text; 
     let userPassword = userPassTextField.text; 
     let userRepeatPassword = userRepeatPasswordTextField.text; 


     // Check for empty fields 
     if(userEmail!.isEmpty || userPassword!.isEmpty || userRepeatPassword!.isEmpty){ 

      displayAlertMessage("All fields are required"); 

      return; 
     } 

     // Check if passwords match 
     if(userPassword != userRepeatPassword){ 

      displayAlertMessage("Passwords do not match"); 

      return; 
     } 

     // Store Data 
     NSUserDefaults.standardUserDefaults().setObject(userEmail, forKey: "userEmail"); 
     NSUserDefaults.standardUserDefaults().setObject(userEmail, forKey: "userPassword"); 
     NSUserDefaults.standardUserDefaults().synchronize(); 

     displayAlertMessage("Registration is successful, thank you.") 
    } 

    // Display Alert message with confirmation 
    func displayAlertMessage(userMessage:String){ 

     let myAlert = UIAlertController(title:"Alert",message: userMessage, preferredStyle: UIAlertControllerStyle.Alert); 

     let okAction = UIAlertAction(title:"ok",style: UIAlertActionStyle.Default, handler:nil); 

     myAlert.addAction(okAction); 
     self.presentViewController(myAlert, animated: true, completion: nil); 
    } 

} 

Answer 3

當你有一個嵌套函數，你必須聲明它之前，你可以調用它。在這種情況下，將「displayAlertMessage（userMessage：String）」函數移動到「//檢查空字段」註釋上方，然後它應該進行編譯。