我的設計模式之旅[6]：Adapter Pattern 與 Strategy Pattern 結合 C++/CLI 實作 (物件適配器)

C++/CLI 版本展示相同架構：Grapher 使用 IDrawStrategy，既有繪圖類別實作 IPaint，透過 DrawAdapter（物件適配器）橋接兩介面。

關鍵程式碼片段

interface class IDrawStrategy { void draw(); };
interface class IPaint { void paint(); };

ref class DrawAdapter : public IDrawStrategy {
    IPaint^ _adaptee;
public:
    DrawAdapter(IPaint^ adaptee) : _adaptee(adaptee) {}
    virtual void draw() { _adaptee->paint(); }
};

完整程式碼

#include "stdafx.h"
using namespace System;

interface class IDrawStrategy { void draw(); };

ref class Grapher {
    IDrawStrategy^ _drawStrategy;
public:
    Grapher() : _drawStrategy(nullptr) {}
    Grapher(IDrawStrategy^ ds) : _drawStrategy(ds) {}
    void drawShape() { if (_drawStrategy != nullptr) _drawStrategy->draw(); }
    void setShape(IDrawStrategy^ ds) { _drawStrategy = ds; }
};

interface class IPaint { void paint(); };

ref class Triangle : public IPaint {
public: virtual void paint() { Console::WriteLine("Draw Triangle"); }
};
ref class Circle : public IPaint {
public: virtual void paint() { Console::WriteLine("Draw Circle"); }
};
ref class Square : public IPaint {
public: virtual void paint() { Console::WriteLine("Draw Square"); }
};

ref class DrawAdapter : public IDrawStrategy {
    IPaint^ _adaptee;
public:
    DrawAdapter() : _adaptee(nullptr) {}
    DrawAdapter(IPaint^ adaptee) : _adaptee(adaptee) {}
    virtual void draw() { _adaptee->paint(); }
};

int main() {
    Grapher^ grapher = gcnew Grapher(gcnew DrawAdapter(gcnew Triangle()));
    grapher->drawShape();
    grapher->setShape(gcnew DrawAdapter(gcnew Circle()));
    grapher->drawShape();
    grapher->setShape(gcnew DrawAdapter(gcnew Square()));
    grapher->drawShape();
}

C++/CLI 同時支援 ISO C++ Template 與 CLI Generics，是 .NET 語言中泛型能力最強者，後續文章將展示其 Template 版類別適配器改良。