NSNotificationCenter 问题：抛出致命错误

Question

我正在开发一个身份验证系统。目前我可以提取 API 数据并对用户进行身份验证。我使用 NSNotificationCenter 字典来存储我的值，我可以打印出字符串消息，但我的布尔值 returns 是可选的。另外，我不确定完成后应该在哪里移除我的观察者。我应该如何实施它？

接收用户输入的代码

import UIKit

class LoginViewController: UIViewController {


@IBOutlet weak var usernameField: UITextField!

@IBOutlet weak var pwdField: UITextField!

@IBAction func loginBtn(sender: AnyObject) {

    let loginobj = Login(userName : self.usernameField.text!, passWord : self.pwdField.text!)
    NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(LoginViewController.handlingAuthentication(_:)), name:"errorPresent", object: nil)
    loginobj.getRequest()

}

override func viewDidLoad() {
    super.viewDidLoad()

}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
}

func handlingAuthentication(notification: NSNotification) {

    let dict = notification.object as! NSDictionary
    let errorFound = dict["error"]
    let errorMessage = dict["message"]
    print(errorFound)

    if((errorFound?.string)! == true){
         //initialize Alert Controller
        let alertController = UIAlertController(title: "Authentication error", message: errorMessage?.string, preferredStyle: .Alert)

        //Initialize Actions
        let okAction = UIAlertAction(title: "Ok", style: .Default){
                (action) -> Void in
                self.dismissViewControllerAnimated(true, completion: nil)
            }

        //Add Actions
        alertController.addAction(okAction)

        //Present Alert Controller
        self.presentViewController(alertController, animated: true, completion: nil)

    }
    else
    {
        NSUserDefaults.standardUserDefaults().setBool(true, forKey: "isUserLoggedIn")

        NSUserDefaults.standardUserDefaults().synchronize()

        self.dismissViewControllerAnimated(true, completion:nil)

    }

}

}

LoginViewController 的代码处理数据处理

import Foundation
import Alamofire
import SwiftyJSON
import RealmSwift

class Login {

init(userName: String, passWord: String) {
    Data.sharedInstance.userName = userName
    Data.sharedInstance.passWord = passWord
}

// call this method to login
func getRequest() {

    Alamofire.request(.POST, Data.todoEndpoint, parameters: ["username": Data.sharedInstance.userName!, "password": Data.sharedInstance.passWord!])
        .responseJSON { response in

            var errorFound = Bool()
            var errorMessage = String()

            if let result = response.result.value
            {
                let value = JSON(result)
                var outcome = String()

                //No username
                if value["password"] == nil && value["message"] == nil && value["name"] == nil
                {
                      errorFound = true
                      outcome = "No username: \(value)"
                      errorMessage = outcome
                }
                //No password
                else if value["username"] == nil && value["message"] == nil
                {
                    errorFound = true
                    outcome = "No password: \(value)"
                    errorMessage = outcome
                }
                //No password/ username
                else if value["username"] == nil && value["password"] == nil && value["message"] != nil
                {
                    outcome = "Incorrect cred: \(value)"
                    errorFound = true
                    errorMessage = outcome
                }
                //success
                else if value["username"] != nil && value["password"] == nil && value["message"] == nil
                {
                    errorFound = false
                    if let api_key = value["api_token"].string
                    {
                        print("The token is " + api_key)
                    }
                    else
                    {
                        print("error parsing api token")
                    }
                    //pass data to Users class
                    _ = Users.init(Name: value["name"].string, Email: value["email"].string, Id: value["id"].int, ProfilePicture: value["profile_picture"].string, Username: value["username"].string)
                    NSNotificationCenter.defaultCenter().removeObserver(self, name: "errorPresent", object: nil)

                }
                else
                {
                    errorFound = true
                    outcome = "No password and username: \(value)"
                    errorMessage = outcome

                }

            }
            else
            {
                print("JSON data is nil.")
            }

                let errorDict = ["error": errorFound, "message": errorMessage]

                NSNotificationCenter.defaultCenter().postNotificationName("errorPresent", object:errorDict)

    }

}


}

Answer 1

正如 Dan 所指出的，一旦网络请求完成，'in' 之后的代码将运行异步。在该代码中触发一个事件（例如 NSNotification），您的其余代码可以使用该事件来知道它已完成。

编辑以回答更改后的问题：在设置变量之前，您仍在 post 发送通知。将 post 移动到 'in' 块的末尾。

编辑 2：关于 nil 错误，我认为这与您对 .string 的使用有关，请参阅

Answer 2

您没有收到所需的布尔结果的原因有两个：

你处理传递的数据的方式是错误的

在您的 handlingAuthentication 方法中，您应该改为这样做：

func handlingAuthentication(notification: NSNotification) {

    let dict = notification.object as! NSDictionary

        if dict["error"]! as! Bool == true {

            let errorMessage = dict["message"] as! String

            //initialize Alert Controller
            let alertController = UIAlertController(title: "Authentication error", message: errorMessage, preferredStyle: .Alert)

            //Initialize Actions
            let okAction = UIAlertAction(title: "Ok", style: .Default){
                    (action) -> Void in
                    self.dismissViewControllerAnimated(true, completion: nil)
            }

            //Add Actions
            alertController.addAction(okAction)

            //Present Alert Controller
            self.presentViewController(alertController, animated: true, completion: nil)

         }

         else

         {

                NSUserDefaults.standardUserDefaults().setBool(true, forKey: "isUserLoggedIn")

                NSUserDefaults.standardUserDefaults().synchronize()

                self.dismissViewControllerAnimated(true, completion:nil)

         }

}

其中 let errorMessage = dict["message"] as! String 和 dict["error"]! as! Bool == true 将从您的输出中删除可选项

您处理 JSON 的方式不正确。据我从您的其他帖子中了解到，您要查找的数据是数组形式的。

这是获取密码和用户名错误值的方法：

 errorMessage = value["password"][0].string!
 errorMessage = value["username"][0].string!

NSNotificationCenter 问题：抛出致命错误

NSNotificationCenter issue: Fatal error thrown

authentication

if-statement

instance-variables

ios

swift2