面向对象设计的SOLID原则

向右看齐 2022-08-20 08:29 178阅读 0赞

# [面向对象设计的SOLID原则][SOLID] #

S.O.L.I.D是面向对象设计和编程(OOD&OOP)中几个重要编码原则(Programming Priciple)的首字母缩写。

<table> 
 <tbody> 
  <tr> 
   <td><strong>SRP</strong></td> 
   <td><a href="http://www.objectmentor.com/resources/articles/srp.pdf" rel="nofollow">The Single Responsibility Principle</a></td> 
   <td>单一责任原则</td> 
  </tr> 
  <tr> 
   <td><strong>OCP</strong></td> 
   <td><a href="http://www.objectmentor.com/resources/articles/ocp.pdf" rel="nofollow">The Open Closed Principle</a></td> 
   <td>开放封闭原则</td> 
  </tr> 
  <tr> 
   <td><strong>LSP</strong></td> 
   <td><a href="http://www.objectmentor.com/resources/articles/lsp.pdf" rel="nofollow">The Liskov Substitution Principle</a></td> 
   <td>里氏替换原则</td> 
  </tr> 
  <tr> 
   <td><strong>DIP</strong></td> 
   <td><a href="http://www.objectmentor.com/resources/articles/dip.pdf" rel="nofollow">The Dependency Inversion Principle</a></td> 
   <td>依赖倒置原则</td> 
  </tr> 
  <tr> 
   <td><strong>ISP</strong></td> 
   <td><a href="http://www.objectmentor.com/resources/articles/isp.pdf" rel="nofollow">The Interface Segregation Principle</a></td> 
   <td>接口分离原则</td> 
  </tr> 
 </tbody> 
</table>

[Steve Smith][]在5月份的微软TechED 2009上有个[SOLIDify Your ASP.NET MVC][]的讲座,[derick.bailey][]的[SOLID Development Principles – In Motivational Pictures][SOLID Development Principles _ In Motivational Pictures]很好的解释了SOLID原则。

**单一责任原则：**  
当需要修改某个类的时候原因有且只有一个（THERE SHOULD NEVER BE MORE THAN ONE REASON FOR A CLASS TO CHANGE）。换句话说就是让一个类只做一种类型责任，当这个类需要承当其他类型的责任的时候，就需要分解这个类。  
 [![SingleResponsibilityPrinciple2\_71060858][SingleResponsibilityPrinciple2_71060858]][SingleResponsibilityPrinciple2_71060858_SingleResponsibilityPrinciple2_71060858]

**开放封闭原则**  
软件实体应该是可扩展，而不可修改的。也就是说，对扩展是开放的，而对修改是封闭的。这个原则是诸多面向对象编程原则中最抽象、最难理解的一个。

[![OpenClosedPrinciple2\_2C596E17][OpenClosedPrinciple2_2C596E17]][OpenClosedPrinciple2_2C596E17_OpenClosedPrinciple2_2C596E17]

**里氏替换原则**  
    里氏替换原则，OCP作为OO的高层原则，主张使用“抽象(Abstraction)”和“多态(Polymorphism)”将设计中的静态结构改为动态结构，维持设计的封闭性。“抽象”是语言提供的功能。“多态”由继承语义实现。  
  
    里氏替换原则(Liskov Substitution Principle LSP)面向对象设计的基本原则之一。 里氏替换原则中说，任何基类可以出现的地方，子类一定可以出现。 LSP是继承复用的基石，只有当衍生类可以替换掉基类，软件单位的功能不受到影响时，基类才能真正被复用，而衍生类也能够在基类的基础上增加新的行为。  
  
    如此，问题产生了：“我们如何去度量继承关系的质量？”  
      
    Liskov于1987年提出了一个关于继承的原则“Inheritance should ensure that any property proved about supertype objects also holds for subtype objects.”——“继承必须确保超类所拥有的性质在子类中仍然成立。”也就是说，当一个子类的实例应该能够替换任何其超类的实例时，它们之间才具有is-A关系。  
  
    该原则称为Liskov Substitution Principle——里氏替换原则。林先生在上课时风趣地称之为“老鼠的儿子会打洞”。^\_^  
[![LiskovSubtitutionPrinciple\_52BB5162][LiskovSubtitutionPrinciple_52BB5162]][LiskovSubtitutionPrinciple_52BB5162_LiskovSubtitutionPrinciple_52BB5162]   
**依赖倒置原则**  
1. 高层模块不应该依赖于低层模块，二者都应该依赖于抽象  
2. 抽象不应该依赖于细节，细节应该依赖于抽象   
[![DependencyInversionPrinciple\_0278F9E2][DependencyInversionPrinciple_0278F9E2]][DependencyInversionPrinciple_0278F9E2_DependencyInversionPrinciple_0278F9E2]

**接口分离原则**  
不能强迫用户去依赖那些他们不使用的接口。换句话说，使用多个专门的接口比使用单一的总接口总要好。

[![InterfaceSegregationPrinciple\_60216468][InterfaceSegregationPrinciple_60216468]][InterfaceSegregationPrinciple_60216468_InterfaceSegregationPrinciple_60216468]

这几条原则是非常基础而且重要的面向对象设计原则。正是由于这些原则的基础性，理解、融汇贯通这些原则需要不少的经验和知识的积累。上述的图片很好的注释了这几条原则。

[SOLID]: http://www.cnblogs.com/shanyou/archive/2009/09/21/1570716.html
[Steve Smith]: http://stevesmithblog.com/
[SOLIDify Your ASP.NET MVC]: http://stevesmithblog.com/blog/teched-2009-session-aftermath/
[derick.bailey]: http://www.lostechies.com/members/derick.bailey/default.aspx
[SOLID Development Principles _ In Motivational Pictures]: http://www.lostechies.com/blogs/derickbailey/archive/2009/02/11/solid-development-principles-in-motivational-pictures.aspx
[SingleResponsibilityPrinciple2_71060858]: http://images.cnblogs.com/cnblogs_com/shanyou/WindowsLiveWriter/SOLID_6402/SingleResponsibilityPrinciple2_71060858_thumb.jpg
[SingleResponsibilityPrinciple2_71060858_SingleResponsibilityPrinciple2_71060858]: /images/20220731/d77e25083b7a41a490690b64f45afdf0.png
[OpenClosedPrinciple2_2C596E17]: http://images.cnblogs.com/cnblogs_com/shanyou/WindowsLiveWriter/SOLID_6402/OpenClosedPrinciple2_2C596E17_thumb.jpg
[OpenClosedPrinciple2_2C596E17_OpenClosedPrinciple2_2C596E17]: /images/20220731/51ea79b186d247ab9cf5ee190c5a5844.png
[LiskovSubtitutionPrinciple_52BB5162]: http://images.cnblogs.com/cnblogs_com/shanyou/WindowsLiveWriter/SOLID_6402/LiskovSubtitutionPrinciple_52BB5162_thumb.jpg
[LiskovSubtitutionPrinciple_52BB5162_LiskovSubtitutionPrinciple_52BB5162]: /images/20220731/5965ebe7821e4d75b40ba83c53ff4fea.png
[DependencyInversionPrinciple_0278F9E2]: http://images.cnblogs.com/cnblogs_com/shanyou/WindowsLiveWriter/SOLID_6402/DependencyInversionPrinciple_0278F9E2_thumb.jpg
[DependencyInversionPrinciple_0278F9E2_DependencyInversionPrinciple_0278F9E2]: /images/20220731/4966d291952148fca522653aafe4f65d.png
[InterfaceSegregationPrinciple_60216468]: http://images.cnblogs.com/cnblogs_com/shanyou/WindowsLiveWriter/SOLID_6402/InterfaceSegregationPrinciple_60216468_thumb.jpg
[InterfaceSegregationPrinciple_60216468_InterfaceSegregationPrinciple_60216468]: /images/20220731/53419bd658c849be9765d8a809ae71a4.png