Patterns emerge from fundamental principles applied to recurring problems

– Design to interfaces

– Favor composition over inheritance

– Find what varies and encapsulate it

solid principles

– Single Responsibility Principle (应该有且仅有一个原因引起类的变更。简单地说：接口职责应该单一，不要承担过多的职责。)

– Open-Closed Principle (对扩展开放，对修改关闭)

– Liskov Substitution Principle (所有引用基类的地方必须能透明地使用其子类。 这就要求子类的所有相同方法，都必须遵循父类的约定，否则当父类替换为子类时就会出错)

– Interface Segregation Principle (类间的依赖关系应该建立在最小的接口上。简单地说：接口的内容一定要尽可能地小，能有多小就多小。)

– Dependency Inversion Principle (高层模块不应该依赖底层模块，两者都应该依赖其抽象。简单地说，就是说我们应该面向接口编程)

• 单一职责是所有设计原则的基础，开闭原则是设计的终极目标。
• 里氏替换原则强调的是子类替换父类后程序运行时的正确性，它用来帮助实现开闭原则。
• 而接口隔离原则用来帮助实现里氏替换原则，同时它也体现了单一职责。
• 依赖倒置原则是过程式编程与面向对象编程的分水岭，同时它也被用来指导接口隔离原则。

Classification of patterns

• Creational patterns provide object creation mechanisms that increase flexibility and reuse of existing code.
• Structural patterns explain how to assemble objects and classes into larger structures, while keeping these structures flexible and efficient.
• Behavioral patterns take care of effective communication and the assignment of responsibilities between objects.

总共23种

Criticism of patterns

Kludges for a weak programming language **

Usually the need for patterns arises when people choose a programming language or a technology that lacks the necessary level of abstraction. In this case, patterns become a kludge that gives the language much-needed super-abilities.

For example, the Strategy pattern can be implemented with a simple anonymous (lambda) function in most modern programming languages.

Unjustified use

If all you have is a hammer, everything looks like a nail.

参考： refactoring.guru/design-patt… zhuanlan.zhihu.com/p/350291336