在Objective-C中通过NSNotificationCenter发送和接收消息?

@implementation TestClass


- (void) dealloc
{
// If you don't remove yourself as an observer, the Notification Center
// will continue to try and send notification objects to the deallocated
// object.
[[NSNotificationCenter defaultCenter] removeObserver:self];
[super dealloc];
}


- (id) init
{
self = [super init];
if (!self) return nil;


// Add this instance of TestClass as an observer of the TestNotification.
// We tell the notification center to inform us of "TestNotification"
// notifications using the receiveTestNotification: selector. By
// specifying object:nil, we tell the notification center that we are not
// interested in who posted the notification. If you provided an actual
// object rather than nil, the notification center will only notify you
// when the notification was posted by that particular object.


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


return self;
}


- (void) receiveTestNotification:(NSNotification *) notification
{
// [notification name] should always be @"TestNotification"
// unless you use this method for observation of other notifications
// as well.


if ([[notification name] isEqualToString:@"TestNotification"])
NSLog (@"Successfully received the test notification!");
}


@end

．.． 在另一门课的某个地方……

- (void) someMethod
{


// All instances of TestClass will be notified
[[NSNotificationCenter defaultCenter]
postNotificationName:@"TestNotification"
object:self];


}

要扩展dreamlax的例子…如果您希望将数据与通知一起发送

邮政编码:

NSDictionary *userInfo =
[NSDictionary dictionaryWithObject:myObject forKey:@"someKey"];
[[NSNotificationCenter defaultCenter] postNotificationName:
@"TestNotification" object:nil userInfo:userInfo];

在观察代码时:

- (void) receiveTestNotification:(NSNotification *) notification {


NSDictionary *userInfo = notification.userInfo;
MyObject *myObject = [userInfo objectForKey:@"someKey"];
}

这条帮助了我:

// Add an observer that will respond to loginComplete
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(showMainMenu:)
name:@"loginComplete" object:nil];




// Post a notification to loginComplete
[[NSNotificationCenter defaultCenter] postNotificationName:@"loginComplete" object:nil];




// the function specified in the same class where we defined the addObserver
- (void)showMainMenu:(NSNotification *)note {
NSLog(@"Received Notification - Someone seems to have logged in");
}

也有可能使用块:

NSOperationQueue *mainQueue = [NSOperationQueue mainQueue];
[[NSNotificationCenter defaultCenter]
addObserverForName:@"notificationName"
object:nil
queue:mainQueue
usingBlock:^(NSNotification *notification)
{
NSLog(@"Notification received!");
NSDictionary *userInfo = notification.userInfo;


// ...
}];

苹果的文档

如果你正在使用NSNotificationCenter来更新你的视图，不要忘记通过调用dispatch_async从主线程发送它:

dispatch_async(dispatch_get_main_queue(),^{
[[NSNotificationCenter defaultCenter] postNotificationName:@"my_notification" object:nil];
});

SWIFT 5.1为新手选择答案

class TestClass {
deinit {
// If you don't remove yourself as an observer, the Notification Center
// will continue to try and send notification objects to the deallocated
// object.
NotificationCenter.default.removeObserver(self)
}


init() {
super.init()


// Add this instance of TestClass as an observer of the TestNotification.
// We tell the notification center to inform us of "TestNotification"
// notifications using the receiveTestNotification: selector. By
// specifying object:nil, we tell the notification center that we are not
// interested in who posted the notification. If you provided an actual
// object rather than nil, the notification center will only notify you
// when the notification was posted by that particular object.


NotificationCenter.default.addObserver(self, selector: #selector(receiveTest(_:)), name: NSNotification.Name("TestNotification"), object: nil)
}


@objc func receiveTest(_ notification: Notification?) {
// [notification name] should always be @"TestNotification"
// unless you use this method for observation of other notifications
// as well.


if notification?.name.isEqual(toString: "TestNotification") != nil {
print("Successfully received the test notification!")
}
}
}

．.． 在另一门课的某个地方……

 func someMethod(){
// All instances of TestClass will be notified
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "TestNotification"), object: self)
}