Observer Pattern

• Observer Pattern

23 种设计模式之一

What problems can the Observer design pattern solve

• A one-to-many dependency between objects should be defined without making the objects tightly coupled.
• It should be ensured that when one object changes state an open-ended number of dependent objects are updated automatically.
• It should be possible that one object can notify an open-ended number of other objects.

What solution does the Observer design pattern describe

• Define Subject and Observer objects.
• so that when a subject changes state,all registered observers are notified and updated automatically.