我的Design Pattern之旅[7]：使用泛型改進Adapter Pattern(OO)(4)

也就是說，C#不允許繼承泛型，CLI的語言C#、VB、C++/CLI的Generics都無法用這個技巧，但C#卻可用『組合泛型』的方式完成。

C# by Generics

/**//*
(C) OOMusou 2007 http://oomusou.cnblogs.com

Filename　　: DP_AdpaterPattern_Strategy_ClassByGenerics.cs
Compiler　　: Visual Studio 2005 / C# 2.0
Description : Demo how to use Strategy Pattern with Adpater Pattern (Class Adapter) By Template
Release　　 : 07/11/2007 1.0
*/
using System;

interface IDrawStrategy {
　void draw();
}

class Grapher {
　protected IDrawStrategy _drawStrategy;

　public Grapher() { }
　public Grapher(IDrawStrategy drawStrategy) {
　　_drawStrategy = drawStrategy;
　}

　public void drawShape() {
　　if (_drawStrategy != null)
　　　_drawStrategy.draw();
　}

　public void setShape(IDrawStrategy drawStrategy) {
　　_drawStrategy = drawStrategy;
　}
}

interface IPaint {
　void paint();
}

class Triangle : IPaint {
　public void paint() {
　　Console.WriteLine("Draw Triangle");
　}
}

class Circle : IPaint {
　public void paint() {
　　Console.WriteLine("Draw Circle");
　}
};

class Square : IPaint {
　public void paint() {
　　Console.WriteLine("Draw Square");
　}
}

class DrawAdapter<T> : IDrawStrategy where T : IPaint, new() {
　protected T _adaptee = new T();

　public void draw() {
　　_adaptee.paint();
　}
}

class ClIEnt {
　static void Main() {
　　Grapher grapher = new Grapher(new DrawAdapter<Triangle>());
　　grapher.drawShape();

　　grapher.setShape(new DrawAdapter<Circle>());
　　grapher.drawShape();

　　grapher.setShape(new DrawAdapter<Square>());
　　grapher.drawShape();
　}
}

執行結果

Draw Triangle
Draw Circle
Draw Square

55行

class DrawAdapter<T> : IDrawStrategy where T : IPaint, new() {
　protected T _adaptee = new T();

　public void draw() {
　　_adaptee.paint();
　}
}