What are the applicable scenarios for the observer pattern?

Applicable scenarios for the observer pattern include: 1. When an abstract model has two aspects, one of which depends on the other; 2. When changes to one object require changes to other objects at the same time, without Know how many objects need to be changed; 3. When an object must notify other objects, it cannot assume who the other objects are.

Observer Pattern

Defines a one-to-many dependency relationship between objects. When an object's state changes, all objects that depend on it are notified and automatically updated

Applicability

• When an abstract The model has two aspects, one of which depends on the other. Encapsulate the two in independent objects so that they can be changed and reused independently

• When changes to one object require changes to other objects at the same time, and you do not know the specific How many objects are left to change

• When an object must notify other objects, but it cannot assume who the other objects are. In other words, you don’t know that these objects are tightly coupled

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