The document discusses the observer pattern and iOS NotificationCenter. It explains that the observer pattern uses an event-driven approach to allow objects to register interest in events and be notified when those events occur. It provides code to demonstrate how to use iOS NotificationCenter by defining a notification name, adding an observer to receive notifications, posting a notification, and removing the observer. Potential pros and cons of using NotificationCenter are also mentioned.

1. NotificationCenter
Jintin

2. How to dispatch
Information ?

3. Hollywood Principle

4. Observer Pattern

5. Observer Pattern
• Event Driven
• Easy to write
• Decoupling

6. Observer Pattern
Observer Subject
Register / Unregister
Notify

7. iOS NotificationCenter

8. iOS NotificationCenter
Observer
Notification
CenteraddObserver /
removeObserver
post notification
Subject
Call Selector

9. iOS NotificationCenter
• Define new Notification.Name
• Add Observer to NotificationCenter with callback
Selector by given Notification.Name
• Post event to NotificationCenter with associate
Notification.Name
• Remove Observer when stop listening

10. Code sample
// Define key
let key = Notification.Name("name")
// Register to receive notification
NotificationCenter.default.addObserver(self, selector:
#selector(callback), name: key, object: nil)
// Post notification
NotificationCenter.default.post(name: key, object: nil)
// Stop listening notification
NotificationCenter.default.removeObserver(self, name: key,
object: nil);

11. Pros & Cons
• Easy to write
• Less code
• Decouple
• ….
• Hard to debug
• Hard to maintain
• Leak
• ….

12. Q&A