笔记：Gof设计模式--Template Method

最新推荐文章于 2025-02-08 15:12:56 发布

liujundykx

最新推荐文章于 2025-02-08 15:12:56 发布

阅读量330

点赞数

CC 4.0 BY-SA版权

分类专栏：学习笔记：Gof设计模式文章标签：设计模式 algorithm behavior hook class up

本文链接：https://blog.youkuaiyun.com/liujundykx/article/details/7627454

学习笔记：Gof设计模式专栏收录该内容

22 篇文章

订阅专栏

本文介绍了模板方法设计模式的核心概念及应用方式。该模式定义了算法骨架，将某些步骤推迟到子类实现，允许子类在不改变算法结构的情况下重新定义算法的某些步骤。适用于需要在多个子类中实施不变部分的算法，并允许子类定义行为变化的情况。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

1、意图

Define the skeleton of an algorithm in an operation, deferring somesteps to subclasses. Template Method lets subclasses redefinecertain steps of an algorithm without changing the algorithm'sstructure.

2、适应性

The Template Method pattern should be used

• to implement the invariant parts of an algorithm once and leave it upto subclasses to implement the behavior that can vary.

• when common behavior among subclasses should be factored and localizedin a common class to avoid code duplication. This is a good example of"refactoring to generalize" as described by Opdyke andJohnson [OJ93].
You first identify thedifferences in the existing code and then separate the differencesinto new operations. Finally, you replace the differing code with atemplate method that calls one of these new operations.

• to control subclasses extensions. You can define a template methodthat calls "hook" operations (see Consequences) at specific points,thereby permitting extensions only at those points.

3、结构

4、示例代码

View's DoDisplayhook operation performs the actual drawing. Display callsSetFocus before DoDisplay to set up the drawingstate; Display calls ResetFocus afterwards torelease the drawing state.

void View::Display () { 
 SetFocus(); 
 DoDisplay(); 
 ResetFocus(); 
}

To maintain the invariant, the View's clients always callDisplay, and View subclasses always overrideDoDisplay.

// DoDisplay does nothing in View: 
void View::DoDisplay () { } 

// Subclasses override it to add their specific drawing behavior: 
void MyView::DoDisplay () { 
 // render the view's contents 
}