Ios UIAlertAction未显示传递的消息

我能够成功地在两个类之间传递字符串消息，但我的

UIAlertAction

没有显示消息

代码发送消息

var message = String()

Alamofire.request(.POST, endPoint, headers: Auth_header, parameters: parameters, encoding: .JSON)
        .validate()
        .responseJSON {
        response in

        switch response.result {
        case .Success(let data):
            let value = JSON(data)
            if value["message"].string != nil {
                message = String(value["message"])
                let dic = ["message": message]
                print("hello")
                NSNotificationCenter.defaultCenter().postNotificationName("notification",object: nil, userInfo: dic)
            }

            onCompletion()

        case .Failure(let error):
            print("Request failed with error: \(error)")
            onError?(error)
        }

import UIKit

class TaskDetailsViewController: UIViewController {


@IBAction func submitBtn(sender: AnyObject) {
     loadTasks()
    NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(TaskDetailsViewController.displayMessage(_:)), name: "notification", object: nil)

}

func displayMessage(notification: NSNotification) {

    if let message = notification.userInfo!["message"]{

        //initialize Alert Controller
        let alertController = UIAlertController(title: "Success", message: message.string, preferredStyle: .Alert)
        print(message)
        print("world")
        //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)

    }
}

接收和显示消息的代码

var message = String()

Alamofire.request(.POST, endPoint, headers: Auth_header, parameters: parameters, encoding: .JSON)
        .validate()
        .responseJSON {
        response in

        switch response.result {
        case .Success(let data):
            let value = JSON(data)
            if value["message"].string != nil {
                message = String(value["message"])
                let dic = ["message": message]
                print("hello")
                NSNotificationCenter.defaultCenter().postNotificationName("notification",object: nil, userInfo: dic)
            }

            onCompletion()

        case .Failure(let error):
            print("Request failed with error: \(error)")
            onError?(error)
        }

import UIKit

class TaskDetailsViewController: UIViewController {


@IBAction func submitBtn(sender: AnyObject) {
     loadTasks()
    NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(TaskDetailsViewController.displayMessage(_:)), name: "notification", object: nil)

}

func displayMessage(notification: NSNotification) {

    if let message = notification.userInfo!["message"]{

        //initialize Alert Controller
        let alertController = UIAlertController(title: "Success", message: message.string, preferredStyle: .Alert)
        print(message)
        print("world")
        //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)

    }
}

我的打印输出

hello
  Score created.
world

---

我认为当传递给

UIAlertController

时，您的

消息.string

是

nil

。检查两次

获取信息后打印

信息

，以便了解其中的内容

---

您还可以设置断点来检查是否正在获取数据。

结果表明，我只需要将

message.string

更改为

message as？成功块中我的displayMessage函数中的字符串

：

case .Success(let data):
        let value = JSON(data)
        if let message = value["message"] as? String {  
            print("message")             
            let dic = ["message": message]
            NSNotificationCenter.defaultCenter().postNotificationName("notification",object: nil, userInfo: dic)
        }

在警报控制器演示中：

if let message = notification.userInfo!["message"] as? String {

    //initialize Alert Controller
    let alertController = UIAlertController(title: "Success", message: message, preferredStyle: .Alert)
    print(message)
    print("world")
    //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)

}

---

如果没有出现，问题是消息字符串为零或消息字符串为空字符串（“”）。

NSNotificationCenter.defaultCenter（）.addObserver（self，selector:#selector（TaskDetailsViewController.displayMessage（35;：）、name:“notification”，object:nil）

必须位于

funct displayMessage（notification:NSNotification）中

比如：

func displayMessage(notification: NSNotification){
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(TaskDetailsViewController.displayMessage(_:)), name: "notification", object: nil)
// Your code
}

然后移除观察者：

deinit{
NSNotificationCenter.defaultCenter().removeObserver
}

---

什么意思？显示警报的方法是否存在问题，因为消息可以很好地传递