代码设计原则笔记

简写	原则	中文	备注
SRP	The Single Responsibility Principle	单一职责原则	一个类,只干自己件事
OCP	The Open-Closed Principle	开闭原则	不会对现有的东西造成影响, 使用接口
LSP	The Liskov Substitution Principle	里氏替换原则	子替父也是可行的
DIP	The Dependency Inversion Principle	依赖反转原则	依赖接口,服务上层
ISP	The Interface Segregation Principle	接口隔离原则	为了避免过度使用接口,对接口瘦身

0. 总结

以上5个原则里面,除了LSP这个,其他几个其实都是相互关联的, 例如,你如果不SRP的话, ISP就不好搞

1. 不干太多的事 -> SRP
2. 不打扰前任 -> OCP
3. 我儿子来也行 -> LSP
4. 我要的,你提供 -> DIP
5. 接口虽好,不要贪杯 -> ISP

1. SRP

A class should have only one reason to change

Responsibility: a reason to change

坏	好
modem_java.PNG
sep_modem.PNG

2. OCP

Software entities (classes, modules, functions, etc) should be open for extension, but closed for modification

坏	好
not_oc.PNG
oc.PNG

3. LSP

Subtypes must be substitutable for their base types

rectangle_square_lsp.PNG

IS a is about Behavior

Design by Contract

Specifying Contract in UnitTest

4. DIP

1. High-level modules should not depend on low-level modules. Both should depend on abstractions
2. Abstractions should not depend on details. Details should depend on abstractions

坏	好
no_dip.PNG
dip.PNG

Depend on Abstractions

5. ISP

There are objects that require noncohesive interfaces; however, it suggests that client should not know about them as a single class. Instead

clients should know about abstract base classes that have cohesive interfaces

坏	好
no_isp.PNG
isp.PNG

ref: Agile Software Development Principles Patterns And Practices: section 2