我的Design Pattern之旅[7]：使用泛型改進Adapter Pattern(OO)(2)

從UML可以發現，TriangleDrawAdapter、CircleDrawAdapter和SquareDrawAdapter都不見了，只剩下一個DrawAdapter，為什麽可以這樣子呢?因為Class Adapter的致命傷就是得繼承Adaptee，這是很強的coupling，利用泛型，我們將繼承的class變成泛型的參數

70行

template<typename T>
class DrawAdapter : public IDrawStrategy, private T {
public:
　virtual void draw() const;
};

這樣就可以在ClIEnt動態的以Adaptee為泛型參數傳入Class Adapter

int main() {
　Grapher grapher(&DrawAdapter<Triangle>());
　grapher.drawShape();

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

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

C++/CLI

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

Filename　　: DP_AdpaterPattern_Strategy_ClassByTemplate.cpp
Compiler　　: Visual C++ 8.0 / BCB 6.0 / gcc 3.4.2 / ISO C++
Description : Demo how to use Strategy Pattern with Adpater Pattern (Class Adapter) By Template
Release　　 : 07/12/2007 1.0
*/
#include "stdafx.h"
using namespace System;

interface class IDrawStrategy {
　void draw();
};

ref class Grapher {
public:
　Grapher() : _drawStrategy(nullptr) {}
　Grapher(IDrawStrategy^ drawStrategy) : _drawStrategy(drawStrategy) {}

public:
　void drawShape();
　void setShape(IDrawStrategy^ drawStrategy);

protected:
　IDrawStrategy^ _drawStrategy;
};

void Grapher::drawShape() {
　if (_drawStrategy != nullptr)
　　　_drawStrategy->draw();
}

void Grapher::setShape(IDrawStrategy^ drawStrategy) {
　_drawStrategy = drawStrategy;
}

interface class IPaint {
　void paint();
};

ref class Triangle : public IPaint {
public:
　virtual void paint();
};

void Triangle::paint() {
　Console::WriteLine("Draw Triangle");
}

ref class Circle : public IPaint {
public:
　virtual void paint();
};

void Circle::paint() {
　Console::WriteLine("Draw Circle");
}

ref class Square : public IPaint {
public:
　virtual void paint();
};

void Square::paint() {
　Console::WriteLine("Draw Square");
}

template<typename T>
ref class DrawAdapter : public IDrawStrategy, public T {
public:
　virtual void draw();
};

template<typename T>
void DrawAdapter<T>::draw() {
　paint();
}

int main() {
　Grapher^ grapher = gcnew Grapher(gcnew DrawAdapter<Triangle>);
　grapher->drawShape();

　grapher->setShape(gcnew DrawAdapter<Circle>);
　grapher->drawShape();

　grapher->setShape(gcnew DrawAdapter<Square>);
　grapher->drawShape();
}

執行結果

Draw Triangle
Draw Circle
Draw Square