如何使用 NSNotificationCenter 传递对象

Question

我正在尝试将一个对象从我的应用委托传递给另一个类中的通知接收器。

我想传递整数messageTotal。现在我有：

在接收器中：

- (void) receiveTestNotification:(NSNotification *) notification
{
    if ([[notification name] isEqualToString:@"TestNotification"])
        NSLog (@"Successfully received the test notification!");
}

- (void)viewDidLoad {
    [super viewDidLoad];

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(dismissSheet) name:UIApplicationWillResignActiveNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(receiveTestNotification:) name:@"eRXReceived" object:nil];

在发出通知的类中：

[UIApplication sharedApplication].applicationIconBadgeNumber = messageTotal;
[[NSNotificationCenter defaultCenter] postNotificationName:@"eRXReceived" object:self];

但我想将对象messageTotal 传递给其他类。

Answer 1

您必须使用“userInfo”变体并传递一个包含 messageTotal 整数的 NSDictionary 对象：

NSDictionary* userInfo = @{@"total": @(messageTotal)};

NSNotificationCenter* nc = [NSNotificationCenter defaultCenter];
[nc postNotificationName:@"eRXReceived" object:self userInfo:userInfo];

在接收端，您可以按如下方式访问 userInfo 字典：

-(void) receiveTestNotification:(NSNotification*)notification
{
    if ([notification.name isEqualToString:@"TestNotification"])
    {
        NSDictionary* userInfo = notification.userInfo;
        NSNumber* total = (NSNumber*)userInfo[@"total"];
        NSLog (@"Successfully received test notification! %i", total.intValue);
    }
}

Answer 2

在提供的解决方案的基础上，我认为展示一个传递您自己的自定义数据对象的示例可能会有所帮助（我在此处根据问题将其称为“消息”）。

A 类（发件人）：

YourDataObject *message = [[YourDataObject alloc] init];
// set your message properties
NSDictionary *dict = [NSDictionary dictionaryWithObject:message forKey:@"message"];
[[NSNotificationCenter defaultCenter] postNotificationName:@"NotificationMessageEvent" object:nil userInfo:dict];

B 类（接收者）：

- (void)viewDidLoad
{
    [super viewDidLoad];
    [[NSNotificationCenter defaultCenter]
     addObserver:self selector:@selector(triggerAction:) name:@"NotificationMessageEvent" object:nil];
}

#pragma mark - Notification
-(void) triggerAction:(NSNotification *) notification
{
    NSDictionary *dict = notification.userInfo;
    YourDataObject *message = [dict valueForKey:@"message"];
    if (message != nil) {
        // do stuff here with your message data
    }
}

Answer 3

Swift 2 版本

正如@Johan Karlsson 指出的那样……我做错了。这是使用 NSNotificationCenter 发送和接收信息的正确方法。

首先，我们看一下 postNotificationName 的初始化器：

init(name name: String,
   object object: AnyObject?,
 userInfo userInfo: [NSObject : AnyObject]?)

source

我们将使用userInfo 参数传递我们的信息。 [NSObject : AnyObject] 类型是 Objective-C 的保留。所以，在 Swift 领域，我们需要做的就是传入一个 Swift 字典，其中的键来自 NSObject，值可以是 AnyObject。

有了这些知识，我们创建了一个字典，我们将把它传递给object 参数：

 var userInfo = [String:String]()
 userInfo["UserName"] = "Dan"
 userInfo["Something"] = "Could be any object including a custom Type."

然后我们将字典传递给我们的对象参数。

发件人

NSNotificationCenter.defaultCenter()
    .postNotificationName("myCustomId", object: nil, userInfo: userInfo)

接收者类

首先我们需要确保我们的班级正在观察通知

override func viewDidLoad() {
    super.viewDidLoad()

    NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("btnClicked:"), name: "myCustomId", object: nil)   
}
    

然后我们可以接收我们的字典：

func btnClicked(notification: NSNotification) {
   let userInfo : [String:String!] = notification.userInfo as! [String:String!]
   let name = userInfo["UserName"]
   print(name)
}

Answer 4

斯威夫特 5

func post() {
    NotificationCenter.default.post(name: Notification.Name("SomeNotificationName"), 
        object: nil, 
        userInfo:["key0": "value", "key1": 1234])
}

func addObservers() {
    NotificationCenter.default.addObserver(self, 
        selector: #selector(someMethod), 
        name: Notification.Name("SomeNotificationName"), 
        object: nil)
}

@objc func someMethod(_ notification: Notification) {
    let info0 = notification.userInfo?["key0"]
    let info1 = notification.userInfo?["key1"]
}

奖金（你绝对应该这样做！）：

将Notification.Name("SomeNotificationName") 替换为.someNotificationName：

extension Notification.Name {
    static let someNotificationName = Notification.Name("SomeNotificationName")
}

将"key0" 和"key1" 替换为Notification.Key.key0 和Notification.Key.key1：

extension Notification {
  enum Key: String {
    case key0
    case key1
  }
}

为什么我一定要这样做？为避免代价高昂的拼写错误，请享受重命名、享受查找用法等...

Answer 5

Swift 5.1 自定义对象/类型

// MARK: - NotificationName
// Extending notification name to avoid string errors.
extension Notification.Name {
    static let yourNotificationName = Notification.Name("yourNotificationName")
}


// MARK: - CustomObject
class YourCustomObject {
    // Any stuffs you would like to set in your custom object as always.
    init() {}
}

// MARK: - Notification Sender Class
class NotificatioSenderClass {

     // Just grab the content of this function and put it to your function responsible for triggering a notification.
    func postNotification(){
        // Note: - This is the important part pass your object instance as object parameter.
        let yourObjectInstance = YourCustomObject()
        NotificationCenter.default.post(name: .yourNotificationName, object: yourObjectInstance)
    }
}

// MARK: -Notification  Receiver class
class NotificationReceiverClass: UIViewController {
    // MARK: - ViewController Lifecycle
    override func viewDidLoad() {
        super.viewDidLoad()
        // Register your notification listener
        NotificationCenter.default.addObserver(self, selector: #selector(didReceiveNotificationWithCustomObject), name: .yourNotificationName, object: nil)
    }

    // MARK: - Helpers
    @objc private func didReceiveNotificationWithCustomObject(notification: Notification){
        // Important: - Grab your custom object here by casting the notification object.
        guard let yourPassedObject = notification.object as? YourCustomObject else {return}
        // That's it now you can use your custom object
        //
        //

    }
      // MARK: - Deinit
  deinit {
      // Save your memory by releasing notification listener
      NotificationCenter.default.removeObserver(self, name: .yourNotificationName, object: nil)
    }




}