接口部分

@interface NotificationCenter : NSObject

+ (void)postNotificationWithName:(NSString *)notificationName;

+ (void)postNotificationWithName:(NSString *)notificationName param:(NSDictionary * __nullable)param;

+ (id <NSObject>)addNotificationOnMainQueueWithName:(NSString *)notificationName block:(void (^)(NSDictionary * __nullable param))block;

+ (void)removeObserver:(id)observer;

+ (void)removeObserver:(id)observer name:(NSString *)name;

+ (void)addNotificationWithObserver:(id)observer selector:(SEL)aSelector name:(nullable NSNotificationName)aName;

@end

实现部分

@implementation NotificationCenter

+ (void)postNotificationWithName:(NSString *)notificationName
{
    [self postNotificationWithName:notificationName param:nil];
}
+ (void)postNotificationWithName:(NSString *)notificationName param:(NSDictionary *)param
{
    [[NSNotificationCenter defaultCenter] postNotificationName:notificationName object:nil userInfo:param];
}

+ (id <NSObject>)addNotificationOnMainQueueWithName:(NSString *)notificationName block:(void (^)(NSDictionary * __nullable param))block
{
    return [[NSNotificationCenter defaultCenter] addObserverForName:notificationName object:nil queue:[NSOperationQueue mainQueue] usingBlock:^(NSNotification * _Nonnull note) {
        NSDictionary *userInfo = note.userInfo;
        block(userInfo);
    }];
}
+ (void)removeObserver:(id)observer
{
    if (observer) {
        [[NSNotificationCenter defaultCenter] removeObserver:observer];
    }
}
+ (void)removeObserver:(id)observer name:(NSString *)name
{
    if (observer) {
        [[NSNotificationCenter defaultCenter] removeObserver:observer name:name object:nil];
    }
}
+ (void)addNotificationWithObserver:(id)observer selector:(SEL)aSelector name:(nullable NSNotificationName)aName
{
    [[NSNotificationCenter defaultCenter] addObserver:observer selector:aSelector name:aName object:nil];
}

@end