ios - Xcode 7 + swift 。 "Use of local variable ' _' before its declaration"错误

Question

我在尝试创建检查用户输入和存储数据的函数时遇到上述错误。在我到达此函数 RegisterButtonTapped() 之前，我的项目构建良好。有没有人有一些结构或语法更改可以消除此错误？

   @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

当你有一个嵌套函数时，你必须在调用它之前声明它。在这种情况下，将“displayAlertMessage(userMessage:String)”函数移到“//Check for empty fields”注释上方，然后它应该可以编译。