swift - AWS 认知 : Trying to Alert User of Error

Question

我在捕获 Cognito 注册错误时遇到困难。当 Cognito 返回“UsernameExistsException”、“message”:“User already exists”错误时，我试图提醒用户。下面是我的代码:

self.pool!.signUp(usernameTextField.text!, password: passwordTextField.text!, userAttributes: attributes,   validationData: nil).continue(successBlock: { (task:AWSTask!) in
                // needs to be async so we can ALWAYS return nil for AWSTask
                DispatchQueue.main.async {
                    if task.error != nil {  // some sort of error
                        let myerror = task.error
                        print("\(myerror)")
                        let alert = UIAlertController(title: "Sign Up Error", message: (task.error?.localizedDescription)! as String, preferredStyle: UIAlertControllerStyle.alert)
                        alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.default, handler: nil))
                        self.present(alert, animated: true, completion: nil)
                    }
                    else    {
                        let response: AWSCognitoIdentityUserPoolSignUpResponse = task.result! as AWSCognitoIdentityUserPoolSignUpResponse
                        // NSLog("AWSCognitoIdentityUserPoolSignUpResponse: \(response)")
                        self.user = response.user
                        let alert = UIAlertController(title: "Sign Up Successful", message: "", preferredStyle: UIAlertControllerStyle.alert)
                        alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: { action in self.performSegue(withIdentifier: "confrimationSegue", sender: self) }))
                        self.present(alert, animated: true, completion: nil)

                    }
                }
                return nil
            })

由于某种原因，我无法进入任务。错误!= nil 条件语句。当我强制错误时，错误不会打印出来，并且警报操作不会出现在 View 中。我是否试图在错误的功能中提醒用户？我还能如何检查 cognito 出现的用户名已存在错误。提前致谢。

Answer 1

您正在使用 successBlock，这意味着您设置的 block 只会在注册成功执行时被调用。这就是错误始终为 nil 的原因。

为了避免错误，您应该简单地通过如下方式设置回调:

userPool
    .signUp(user.email, password: user.password, userAttributes: attributes, validationData: nil)
    .continue({ response in
        if let error = response.error {
           // Error ocurred
        } else {
           // No error ocurred
        })

continue 方法只接收回调，并在发生错误时调用。