Smalltalk 语言 类层次重构案例 提取图形父类

Smalltalkamuwap 发布于 6 天前 6 次阅读

阿木博主一句话概括：Smalltalk 语言中图形类层次重构：提取图形父类的设计与实现

阿木博主为你简单介绍：
本文以Smalltalk语言为背景，针对图形类层次结构进行重构，提出了一种提取图形父类的设计方法。通过分析现有图形类层次结构，设计并实现了一个通用的图形父类，从而简化了类层次，提高了代码的可维护性和扩展性。文章将详细介绍重构过程、设计思路以及实现细节。

一、

在图形编程领域，类层次结构是构建图形系统的基础。随着图形系统的复杂度增加，类层次结构可能会变得臃肿，导致代码难以维护和扩展。本文以Smalltalk语言为例，探讨如何通过提取图形父类来重构类层次结构，提高代码质量。

二、现有图形类层次结构分析

在Smalltalk语言中，图形类层次结构通常包含以下类：

1. Shape：图形基类，定义了图形的基本属性和方法。
2. Circle：圆形类，继承自Shape，具有圆形特有的属性和方法。
3. Rectangle：矩形类，继承自Shape，具有矩形特有的属性和方法。
4. Line：直线类，继承自Shape，具有直线特有的属性和方法。

这种结构存在以下问题：

1. 重复代码：Shape类中定义了图形的基本属性和方法，但Circle、Rectangle和Line类中又分别定义了相同的属性和方法。
2. 扩展性差：当需要添加新的图形类型时，需要修改Shape类及其所有子类，增加了维护成本。

三、提取图形父类的设计

为了解决上述问题，我们可以设计一个通用的图形父类，将图形的基本属性和方法集中定义在该类中。以下是设计思路：

1. 创建一个新的类名为Graphic，作为所有图形类的父类。
2. 将Shape类中的基本属性和方法迁移到Graphic类中。
3. 修改Circle、Rectangle和Line类，使其继承自Graphic类。

四、实现细节

1. 创建Graphic类：

```smalltalk
class Graphic
instanceVariableNames: 'x y width height'
classVariableNames: ''
classInstVarNames: ''
classInstVarTypes: ''
classInstVarInitValues: ''
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classVariableInitValues: ''
classVariableReaders: ''
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