CFNotificationCenter

CFNotificationCenter is an object representing a local or remote notification center, which is a singleton object of its type that receives notifications from different sources, and distributes them to the listeners.

Great way to determine various PRIVATE events that may want to subscribe to

Add the observer below in your startup code and implement the callback handler below. Then perform actions on your phone or other apps and log the events you may be interested in.

// Make the callback handler
void notificationCallback(CFNotificationCenterRef center, void *observer, CFStringRef name, const void *object, CFDictionaryRef userInfo) {
	NSLog(@"Callback detected: \n\t name: %@ \n\t object:%@", name, object);
}

void startupFunction() {
    ...
    // Register your handler
    CFNotificationCenterAddObserver(CFNotificationCenterGetLocalCenter(),
                                    NULL,
                                    notificationCallback,
                                    NULL,
                                    NULL,  
                                    CFNotificationSuspensionBehaviorDeliverImmediately);
    ...
}

Hat tip: http://stackoverflow.com/questions/3725234/nsnotificationcenter-trapping-and-tracing-all-nsnotifications/3738387#3738387

Look up all observers of the local center

You can get the dictionary of all observers in the local center by doing this:

CFNotificationCenterRef center = CFNotificationCenterGetLocalCenter();
CFDictionaryRef dict = *(CFDictionaryRef*)(center + 4);
CFShow(dict);

Post notification with objects

DistributedCenter has been silently available since iOS 5. It can send property list objects(NSArray, NSDictionary, NSNumber, NSString, NSDate and NSData) to other processes.

// First, define function as external.
extern CFNotificationCenterRef CFNotificationCenterGetDistributedCenter(void);

// Implement a callback function.
static void CallBackFunction(CFNotificationCenterRef center, void *observer, CFStringRef name, const void *object, CFDictionaryRef userInfo) {
	...
	NSLog(@"Callback detected: \n\t name: %@ \n\t object:%@", name, object);
}

...

void startup() {
	...
	// Check if DistributedCenter is available:
	void *handle = dlopen("/System/Library/Frameworks/CoreFoundation.framework/CoreFoundation", RTLD_LAZY);
	void *impl = NULL;
	if (handle) {
		impl = dlsym(handle, "CFNotificationCenterGetDistributedCenter");
	}
	if (impl) { // Available.
		// Registration in receiver process.
		CFNotificationCenterAddObserver(CFNotificationCenterGetDistributedCenter(),
			NULL,
			CallBackFunction,
			CFSTR("notification.identifier"),
			NULL,
			CFNotificationSuspensionBehaviorDeliverImmediately);
		}
	}
	...
}

...

// Sender
void somewhereElse() {
	...
	CFMutableDictionaryRef dictionary = CFDictionaryCreateMutable(NULL, 0, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
	CFDictionaryAddValue(dictionary, @"key of string", @1);
	CFNotificationCenterPostNotification(CFNotificationCenterGetDistributedCenter(), CFSTR("notification.identifier"), @"string object", dictionary, true);
	CFRelease(dictionary);
	...
}

External links

• Official reference: http://developer.apple.com/iphone/library/documentation/CoreFoundation/Reference/CFNotificationCenterRef/Reference/reference.html