NOTE

Open–Closed Principle

What the open–closed principle is, why it is needed, and how to implement it through abstractions, inheritance, composition, and aggregation.

Software Architecture & EngineeringCreated 08/30/2021Updated 08/30/20211 min readhistorical

This is a historical learning note and may contain outdated or incomplete understanding.

1. What Is the Open–Closed Principle?

Open for extension, closed for modification.

2. Why Is the Open–Closed Principle Needed?

Reduce new risks introduced by maintenance.

3. Implementing the Open–Closed Principle

When modifying code for a new requirement, check whether existing code needs to be modified. If so, refactor it: define an abstraction layer through interfaces or abstract classes, and encapsulate variable factors in concrete implementation classes.

Inheritance: Liskov Substitution Principle.md

Composition/aggregation: Composition Reuse Principle.md

4. References

Open–Closed Principle — Object-Oriented Design Principles

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