Thinking in Design Pattern

Principle in DP:

1. Everything is an object.

    1.1 所有的模式都是围绕对象展开. 解决方案大体可分2类:

    1.1.1 通过Add type, override virtual method, 来适应改变. Factory, decorator 等等众多模式都是如此.

    1.1.2 简单创建对象, 通过对象的自管理来处理变化. Facade, mediator 些许模式如此. 

2. Encapsulating variation.

    When an aspect of a program changes frequently, defining an object that encapsulates that aspect[1].

3. To program to an interface, not an implementation

4. To favor object composition ("has") over class inheritance ("is-a").

 

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Ref:

[1] Design patterns. GOF. Chapter 5, Page 345.