Nsicationicationcenter message center in iOS Design Mode

Nsicationicationcenter message center in iOS Design Mode
The message center mode is similar to the KVO mode. The difference is that the KVO mode is intended to listen to a change in the corresponding value, and proceed with a corresponding action of the method, while the message center is, broadcast: it is like a broadcast base station that sends a message. It can receive this message in all the places where listening is added, and make the same action for different living conditions, with a wider range, more powerful

// Add a message center listener (adding an observer can also be said to add a listener) [[nsicationicationcenter defacenter center] addObserver: self selector: @ selector (myNotification :) name: @ "test1" object: nil];
It monitors whether the entire value of test1 has been sent to the entire message. The Listener is in the self class. If it listens, The myNotification method is triggered.
// Send messages through the message center,
// Note: In the message center, First listen and then send messages
// Object: The sent parameter [[nsicationicationcenter defacenter center] postNotificationName: @ "test1" object: arra];
// This method can be used in any class of this project, so that it can communicate with other places.

// For example, if there are five pages, a message center is created in the first four pages to listen to a message @ "change" // on the fifth page, through the message center, send a @ "change" message, so that the first four pages can receive the message, and then make the corresponding action // be sure to note that the message center listener must be created before sending the message, // The key to solving this problem when using various cyclic functions flexibly


Let's look at an instance.

Two interfaces: interface 1 interface 2 interface 1 create a message center to listen to messages, interface 2-bed message center, send messages with Parameters

// Create a message center in interface 1 [[NSNotificationCenter defacenter center] addObserver: self selector: @ selector (myNotification :) name: @ "test1" object: nil];



In interface 1, implement the listening method // execute this method when listening to messages-(void) myNotification :( NSNotification *) n {// retrieve the object from received message n, that is, the parameters loaded in the message.
// NSString * param = [n object];
NSArray * arr = [n object];
NSLog (@ "% @", arr );
}

In interface 2, send an array as the parameter NSArray * arra = [NSArrayarrayWithObjects: @ "a", @ "d", nil];
// Send messages through the message center,
// Note: In the message center, First listen and then send messages
// Object: The sent parameter [[nsicationicationcenter defacenter center] postNotificationName: @ "test1" object: arra];