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

C# 版物件適配器實作，架構同前：Grapher 依賴 IDrawStrategy，既有類別實作 IPaint，DrawAdapter 組合 IPaint 並轉呼叫 paint()。

完整程式碼

using System;

interface IDrawStrategy { void draw(); }

class Grapher {
    protected IDrawStrategy _drawStrategy = null;
    public Grapher() {}
    public Grapher(IDrawStrategy ds) { _drawStrategy = ds; }
    public void drawShape() { if (_drawStrategy != null) _drawStrategy.draw(); }
    public void setShape(IDrawStrategy ds) { _drawStrategy = ds; }
}

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 : IDrawStrategy {
    protected IPaint _adaptee = null;
    public DrawAdapter() {}
    public DrawAdapter(IPaint adaptee) { _adaptee = adaptee; }
    public void draw() { _adaptee.paint(); }
}

class Client {
    static void Main() {
        Grapher grapher = new Grapher(new DrawAdapter(new Triangle()));
        grapher.drawShape();
        grapher.setShape(new DrawAdapter(new Circle()));
        grapher.drawShape();
        grapher.setShape(new DrawAdapter(new Square()));
        grapher.drawShape();
    }
}

執行結果

Draw Triangle
Draw Circle
Draw Square

物件適配器採用組合而非繼承，單一適配器類別即可處理所有 IPaint 實作，符合「多用組合、少用繼承」原則，且支援執行期動態切換被適配物件。