SOLID原则
面向对象 class 设计的五条原则。他们是设计 class 结构时应该遵守的准则和最佳实践。
- S：Single Responsibility principle 单一职责原则，一个类应该只有一个引起它变化的原因。
- There should never be more than one reason for a class to change.
- In other words, every class should have only one responsibility.
- O：Open–closed principle 开闭原则，类应该对扩展开放对修改关闭。
- Software entities ... should be open for extension, but closed for modification.
- L：Liskov substitution principle 里氏替换，应用程序中任何父类对象出现的地方，我们都可以用其子类的对象来替换，并且可以保证原有程序的逻辑行为和正确性
- Functions that use pointers or references to base classes must be able to use objects of derived classes without knowing it.
- 里氏替换主要说明了针对类继承的规则：如果继承是为了代码复用，则共享的父类方法应该保持不变，子类增加新的方法来扩展功能。如果继承是为了多态，多态的前提就是覆盖并重新定义父类方法，则应该将父类定义为抽象类。
- I：Interface segregation principle 接口隔离，客户端只依赖于它必须的接口，接口中的方法尽量少
- clients should not be forced to depend upon interfaces that they do not use
- D：Dependency inversion principle 依赖倒置，针对接口编程，模块之间依赖抽象
- Dependency inversion principle (DIP) states to depend upon abstractions, not concretes
- 参考：cloud.tencent.com/developer/a…
