XMCNotificationCenter

##English

In iOS between modules communication we use the most is NSNotificationCenter. For example, we now have a module needs to throw out a notice to notify other module user name changed, we look at how to write the code roughly

Send notification
NSString *const kUserNameChangedNotification = @"UserNameChangedNotification";
NSString *const kUserOldNameKey = @"UserOldNameKey";
NSString *const kUserNewNameKey = @"UserNewNameKey";

NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];
[notificationCenter postNotificationName:UserNameChangedNotification object:nil userInfo:@{kUserOldNameKey:@"oldName",UserNewNameKey:"newName"}];

Get notification can be
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(UserNameChanged:) name:kUserNameChangedNotification object:nil];
or can be
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(UserNameChangedNotification:) name:kUserNameChangedNotification object:nil];

Examples can be seen from some shortcomings:
1.To receive notification of the same event, different people may use different method name can not be unified。
2.Support for multi-parameter convenient。
To Solve these two，I write XMCNotificationCenter

Send Notification
@protocol UserObserver <NSObject>
- (void)userNameChangedWithOldName:(NSString *)oldName newName:(NSString *)newName;
@end
PostNotification(UserObserver, @selector(userNameChangedWithOldName:newName:), userNameChangedWithOldName:@"oldName", newName:@"newName");

Get Notification
AddObserverWithProtocol(self, UserObserver);implement the method userNameChangedWithOldName:newName: in UserObserver Protocol
RemoveObserver(self);

XMCNotificationCenterWhich method small, simple to use, first define protocols such as UserObserver, and add methods which need to implement, as required or optional method can be
Then there is the ruler, just use PostNotification, parameters are SEL of method, method calls (where there will be a prompt for XCode).
Finally is the observer, using AddObserver With Protocol to add your own need to observe the protocol and implemented the method you need, if a method is optional, and you didn't implemented you will not receive notification。
Because a lot of system behavior post by NSNotificationCenter, so XMCNotificationCenter can not completely replace NSNotificationCenter. However, if the notice is post by ourselves, the we can use XMCNotificationCenter

##中文 在iOS中模块间通知我们用得最多的就是NSNotificationCenter。举个例子，现在我们有一个模块需要抛一个通知出来，通知其它模块用户名改变了，我们来看代码大致是怎么写的

发通知一方
NSString *const kUserNameChangedNotification = @"UserNameChangedNotification";
NSString *const kUserOldNameKey = @"UserOldNameKey";
NSString *const kUserNewNameKey = @"UserNewNameKey";

NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];
[notificationCenter postNotificationName:UserNameChangedNotification object:nil userInfo:@{kUserOldNameKey:@"oldName",UserNewNameKey:"newName"}];

接收通知的一方可以是
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(UserNameChanged:) name:kUserNameChangedNotification object:nil];
也可以是
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(UserNameChangedNotification:) name:kUserNameChangedNotification object:nil];

从例子中可以看到有的缺点:
1.对于接收同一个事件的通知，不同的人可能会用不同的方法名，无法统一。
2.对于多参数支持不方便。
出于以上两点，写了这个XMCNotificationCenter，对应上面情况会变成以下

发通知一方
@protocol UserObserver <NSObject>
- (void)userNameChangedWithOldName:(NSString *)oldName newName:(NSString *)newName;
@end
PostNotification(UserObserver, @selector(userNameChangedWithOldName:newName:), userNameChangedWithOldName:@"oldName", newName:@"newName");

接收通知的一方是
AddObserverWithProtocol(self, UserObserver);并实现UserObserver协议的userNameChangedWithOldName:newName:方法即可
RemoveObserver(self);

XMCNotificationCenter里面方法不多，使用简单，先定义协议如UserObserver,并添加里面需要实现的方法，方法为required或optional都可以
接下来就是通知者，只要使用PostNotification宏，参数分别是协议、方法的SEL、方法调用（这里还会有XCode的提示输入）。
最后就是观察者，使用AddObserverWithProtocol添加自己需要观察的协议，并实现协议相关方法，如果是optional的方法，不实现也就不会接收到通知。
因为系统很多行为是靠NSNotificationCenter通知出来的,所以XMCNotificationCenter不能完全替代NSNotificationCenter。但如果通知是由我们自己发出，都可以使用XMCNotificationCenter。