removeObserver swizzling added + SWIZZLE_NSNOTIFICATIONCENTER + separate .h and .m files

NSNotificationCenter+AllObservers.h

#import <Foundation/Foundation.h>

@interface NSNotificationCenter (AllObservers)
- (NSSet *) my_observersForNotificationName:(NSString *)notificationName;
@end

NSNotificationCenter+AllObservers.m

#import "NSNotificationCenter+AllObservers.h"
#import <Foundation/Foundation.h>
#import <objc/runtime.h>

@implementation NSNotificationCenter (AllObservers)

const static void *namesKey = &namesKey;

+ (void) load
{
#if (SWIZZLE_NSNOTIFICATIONCENTER)
	method_exchangeImplementations(class_getInstanceMethod(self, @selector(addObserver:selector:name:object:)),
	                               class_getInstanceMethod(self, @selector(my_addObserver:selector:name:object:)));
    method_exchangeImplementations(class_getInstanceMethod(self, @selector(removeObserver:)),
                                   class_getInstanceMethod(self, @selector(my_removeObserver:)));
    method_exchangeImplementations(class_getInstanceMethod(self, @selector(removeObserver:name:object:)),
                                   class_getInstanceMethod(self, @selector(my_removeObserver:name:object:)));
#endif
}

- (void)my_removeObserver:(id)observer name:(NSString *)aName object:(id)anObject {
    NSDictionary *names = [self names];
    [self removeObserver:observer fromNames:names withName:aName];
    [self my_removeObserver:observer name:aName object:anObject];
}

- (void)removeObserver:(id)observer fromNames:(NSDictionary *)names withName:(NSString *)aName {
    NSMutableSet *observers = [names valueForKey:aName];
    if ([observers containsObject:observer]) {
        [observers removeObject:observer];
    }
}

- (void)my_removeObserver:(id)observer {
    if (observer) {
        NSDictionary *names = [self names];
        for (NSString *aName in names) {
            [self removeObserver:observer fromNames:names withName:aName];
        }
    }
    [self my_removeObserver:observer];
}

- (void) my_addObserver:(id)notificationObserver selector:(SEL)notificationSelector name:(NSString *)notificationName object:(id)notificationSender
{
	[self my_addObserver:notificationObserver selector:notificationSelector name:notificationName object:notificationSender];
	
	if (!notificationObserver || !notificationName)
		return;
	
	NSMutableDictionary *names = [self names];
	NSMutableSet *observers = [names objectForKey:notificationName];
	if (!observers)
	{
		observers = [NSMutableSet setWithObject:notificationObserver];
		[names setObject:observers forKey:notificationName];
	}
	else
	{
		[observers addObject:notificationObserver];
	}
}

- (NSMutableDictionary *)names {
    NSMutableDictionary *names = objc_getAssociatedObject(self, namesKey);
	if (!names)
	{
		names = [NSMutableDictionary dictionary];
		objc_setAssociatedObject(self, namesKey, names, OBJC_ASSOCIATION_RETAIN);
	}
    return names;
}

- (NSSet *) my_observersForNotificationName:(NSString *)notificationName
{
	NSMutableDictionary *names = objc_getAssociatedObject(self, namesKey);
	return [names objectForKey:notificationName] ?: [NSSet set];
}

@end