NotificationCenter在Swift中传递数据

Question

我正在研究Swift 3中的测试项目.我正在尝试使用NotificationCenter将textField字符串从一个类传递到另一个类.我试图通过这个链接来解决答案:将NSString变量传递给具有NSNotification的其他类以及如何在swift中传递带有通知的多个值

我从上面的链接尝试了几个答案,但没有任何效果.

我的代码:

//第一个VC

import UIKit


extension Notification.Name {        
public static let myNotificationKey = Notification.Name(rawValue: "myNotificationKey")    
}


class ViewController: UIViewController {

@IBOutlet weak var textView: UITextView!

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 sendData(_ sender: AnyObject) {

    let userInfo = [ "text" : textView.text ]
    NotificationCenter.default.post(name: .myNotificationKey, object: nil, userInfo: userInfo)

}

}

// SecondVC

 import Foundation
 import  UIKit

 class viewTwo: UIViewController {

@IBOutlet weak var result: UILabel!



override func viewDidLoad() {


}


override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    NotificationCenter.default.addObserver(self, selector: #selector(self.notificationReceived(_:)), name: .myNotificationKey, object: nil)
}

override func viewDidDisappear(_ animated: Bool) {
    super.viewDidDisappear(animated)
    NotificationCenter.default.removeObserver(self, name: .myNotificationKey, object: nil)
}

func notificationReceived(_ notification: Notification) {
    guard let text = notification.userInfo?["text"] as? String else { return }
    print ("text: \(text)")

    result.text = text
}

}

我不确定代码有什么问题.上面,代码最初标记为答案,我从第一个链接中找到.代码已转换为Swift.

Answer 1

不要使用object参数传递数据.它旨在过滤具有相同名称但来自特定对象的通知.因此,如果在addObserver发布通知和另一个对象时传递了一些对象,则不会收到它.如果你传递nil,你基本上会关闭这个过滤器.

你应该使用userInfo参数.

首先,最好将通知的名称定义为Notification.Name的扩展名.这种方法更安全,更易读:

extension Notification.Name {        
    public static let myNotificationKey = Notification.Name(rawValue: "myNotificationKey")    
}

发布通知:

let userInfo = [ "text" : text ]
NotificationCenter.default.post(name: .myNotificationKey, object: nil, userInfo: userInfo)

订阅:

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    NotificationCenter.default.addObserver(self, selector: #selector(self.notificationReceived(_:)), name: .myNotificationKey, object: nil)
}

退订:

override func viewDidDisappear(_ animated: Bool) {
    super.viewDidDisappear(animated)
    NotificationCenter.default.removeObserver(self, name: .myNotificationKey, object: nil)
}

要调用的方法:

func notificationReceived(_ notification: Notification) {
    guard let text = notification.userInfo?["text"] as? String else { return }
    print ("text: \(text)")
}

Answer 2

使用userInfo哪个是 [AnyHashable:Any] 类型的可选字典传递文本？在 Swift 3.0 中，它是 [NSObject : AnyObject]？在 swift 2.0

@IBAction func sendData(_ sender: UIButton) {

// post a notification
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "notificationName"), object: nil, userInfo: ["text": textValue.text])

print(textValue) // textValue printing

}

在 viewDidLoad

//注册接收通知

NotificationCenter.default.addObserver(self, selector: #selector(self. incomingNotification(_:)), name:  NSNotification.Name(rawValue: "notificationName"), object: nil)

并在传入通知中

func incomingNotification(_ notification: Notification) {
if let text = notification.userInfo?["text"] as? String {
   print(text)
  // do something with your text   
}


}

Answer 3

在您的sendData方法中传递textField.text到通知对象并在您incomingNotification执行此操作：

guard let theString = notification.object as? String else {
    print("something went wrong")
    return 
}

resultLabel.text = theString

您还可以使用块在控制器之间传递数据。