橋接模式

橋接模式是軟件設計模式中最複雜的模式之一，它把事物對象和其具體行爲、具體特徵分離開來，使它們可以各自獨立的變化。事物對象僅是一個抽象的概念。如「圓形」、「三角形」歸於抽象的「形狀」之下，而「畫圓」、「畫三角」歸於實現行爲的「畫圖」類之下，然後由「形狀」調用「畫圖」。

結構

Abstraction

定義抽象的介面

該介面包含實現具體行爲、具體特徵的Implementor介面

Refined Abstraction

抽象介面Abstraction的子類，依舊是一個抽象的事物名

Implementor

定義具體行爲、具體特徵的應用介面

ConcreteImplementor

實現Implementor介面

示例

下列各語言的代碼都用於寫出兩個不同的圓的坐標和半徑。

API1.circle at 1:2 7.5
API2.circle at 5:7 27.5

Java

/** "Implementor" */
interface DrawingAPI
{
    public void drawCircle(double x, double y, double radius);
}

/** "ConcreteImplementor" 1/2 */
class DrawingAPI1 implements DrawingAPI
{
   public void drawCircle(double x, double y, double radius) 
   {
        System.out.printf("API1.circle at %f:%f radius %f\n", x, y, radius);
   }
}

/** "ConcreteImplementor" 2/2 */
class DrawingAPI2 implements DrawingAPI
{
   public void drawCircle(double x, double y, double radius) 
   { 
        System.out.printf("API2.circle at %f:%f radius %f\n", x, y, radius);
   }
}

/** "Abstraction" */
interface Shape
{
   public void draw();                                            // low-level
   public void resizeByPercentage(double pct);     // high-level
}

/** "Refined Abstraction" */
class CircleShape implements Shape
{
   private double x, y, radius;
   private DrawingAPI drawingAPI;
   public CircleShape(double x, double y, double radius, DrawingAPI drawingAPI)
   {
       this.x = x;  this.y = y;  this.radius = radius; 
       this.drawingAPI = drawingAPI;
   }

   // low-level i.e. Implementation specific
   public void draw()
   {
        drawingAPI.drawCircle(x, y, radius);
   }   
   // high-level i.e. Abstraction specific
   public void resizeByPercentage(double pct)
   {
        radius *= pct;
   }
}

/** "Client" */
class BridgePattern {
   public static void main(String[] args)
   {
       Shape[] shapes = new Shape[2];
       shapes[0] = new CircleShape(1, 2, 3, new DrawingAPI1());
       shapes[1] = new CircleShape(5, 7, 11, new DrawingAPI2());

       for (Shape shape : shapes)
       {
           shape.resizeByPercentage(2.5);
           shape.draw();
       }
   }
}

C#

 using System;
 
 /** "Implementor" */
 interface IDrawingAPI {
    void DrawCircle(double x, double y, double radius);
 }
 
 /** "ConcreteImplementor" 1/2 */
 class DrawingAPI1 : IDrawingAPI {
    public void DrawCircle(double x, double y, double radius) 
    {
        System.Console.WriteLine("API1.circle at {0}:{1} radius {2}", x, y, radius); 
    }
 }
 
 /** "ConcreteImplementor" 2/2 */
 class DrawingAPI2 : IDrawingAPI 
 {
    public void DrawCircle(double x, double y, double radius) 
    { 
        System.Console.WriteLine("API2.circle at {0}:{1} radius {2}", x, y, radius); 
    }
 }
 
 /** "Abstraction" */
 interface IShape {
    void Draw();                             // low-level (i.e. Implementation-specific)
    void ResizeByPercentage(double pct);     // high-level (i.e. Abstraction-specific)
 }
 
 /** "Refined Abstraction" */
 class CircleShape : IShape {
    private double x, y, radius;
    private IDrawingAPI drawingAPI;
    public CircleShape(double x, double y, double radius, IDrawingAPI drawingAPI) 
    {
        this.x = x;  this.y = y;  this.radius = radius; 
        this.drawingAPI = drawingAPI;
    }
    // low-level (i.e. Implementation-specific)
    public void Draw() { drawingAPI.DrawCircle(x, y, radius); }
    // high-level (i.e. Abstraction-specific)
    public void ResizeByPercentage(double pct) { radius *= pct; }
 }
 
 /** "Client" */
 class BridgePattern {
    public static void Main(string[] args) {
        IShape[] shapes = new IShape[2];
        shapes[0] = new CircleShape(1, 2, 3, new DrawingAPI1());
        shapes[1] = new CircleShape(5, 7, 11, new DrawingAPI2());
 
        foreach (IShape shape in shapes) {
            shape.ResizeByPercentage(2.5);
            shape.Draw();
        }
    }
 }

用generics類庫的C#

 using System;
 
 /** "Implementor" */
 interface IDrawingAPI {
    void DrawCircle(double x, double y, double radius);
 }
 
 /** "ConcreteImplementor" 1/2 */
 struct DrawingAPI1 : IDrawingAPI {
    public void DrawCircle(double x, double y, double radius) 
    {
        System.Console.WriteLine("API1.circle at {0}:{1} radius {2}", x, y, radius); 
    }
 }
 
 /** "ConcreteImplementor" 2/2 */
 struct DrawingAPI2 : IDrawingAPI 
 {
    public void DrawCircle(double x, double y, double radius) 
    { 
        System.Console.WriteLine("API2.circle at {0}:{1} radius {2}", x, y, radius); 
    }
 }
 
 /** "Abstraction" */
 interface IShape {
    void Draw();                             // low-level (i.e. Implementation-specific)
    void ResizeByPercentage(double pct);     // high-level (i.e. Abstraction-specific)
 }
 
 /** "Refined Abstraction" */
 class CircleShape<T> : IShape
    where T : struct, IDrawingAPI
 {
    private double x, y, radius;
    private static IDrawingAPI drawingAPI = new T();
    public CircleShape(double x, double y, double radius) 
    {
        this.x = x;  this.y = y;  this.radius = radius;
    }
    // low-level (i.e. Implementation-specific)
    public void Draw() { drawingAPI.DrawCircle(x, y, radius); }
    // high-level (i.e. Abstraction-specific)
    public void ResizeByPercentage(double pct) { radius *= pct; }
 }
 
 /** "Client" */
 class BridgePattern {
    public static void Main(string[] args) {
        IShape[] shapes = new IShape[2];
        shapes[0] = new CircleShape<DrawingAPI1>(1, 2, 3);
        shapes[1] = new CircleShape<DrawingAPI2>(5, 7, 11);
 
        foreach (IShape shape in shapes) {
            shape.ResizeByPercentage(2.5);
            shape.Draw();
        }
    }
 }

C++

#include <iostream>

using namespace std;

/* Implementor*/
class DrawingAPI {
  public:
   virtual void drawCircle(double x, double y, double radius) = 0;
   virtual ~DrawingAPI() {}
};

/* Concrete ImplementorA*/
class DrawingAPI1 : public DrawingAPI {
  public:
   void drawCircle(double x, double y, double radius) {
      cout << "API1.circle at " << x << ':' << y << ' ' << radius << endl;
   }
};

/* Concrete ImplementorB*/
class DrawingAPI2 : public DrawingAPI {
public:
   void drawCircle(double x, double y, double radius) {
      cout << "API2.circle at " << x << ':' << y << ' ' <<  radius << endl;
   }
};

/* Abstraction*/
class Shape {
  public:
   virtual ~Shape() {}
   virtual void draw() = 0;
   virtual void resizeByPercentage(double pct) = 0;
};

/* Refined Abstraction*/
class CircleShape : public Shape {
  public:
   CircleShape(double x, double y,double radius, DrawingAPI *drawingAPI) :
	   m_x(x), m_y(y), m_radius(radius), m_drawingAPI(drawingAPI)
   {}
   void draw() {
      m_drawingAPI->drawCircle(m_x, m_y, m_radius);
   }
   void resizeByPercentage(double pct) {
      m_radius *= pct;
   }
  private:
   double m_x, m_y, m_radius;
   DrawingAPI *m_drawingAPI;
};

int main(void) {
   DrawingAPI1 dap1;
   DrawingAPI2 dap2;
   CircleShape circle1(1,2,3,&dap1);
   CircleShape circle2(5,7,11,&dap2);
   circle1.resizeByPercentage(2.5);
   circle2.resizeByPercentage(2.5);
   circle1.draw();
   circle2.draw();
   return 0;
}

Python

# Implementor
class DrawingAPI:
	def drawCircle(x, y, radius):
		pass

# ConcreteImplementor 1/2
class DrawingAPI1(DrawingAPI):
	def drawCircle(self, x, y, radius):
		print "API1.circle at %f:%f radius %f" % (x, y, radius)

# ConcreteImplementor 2/2
class DrawingAPI2(DrawingAPI):
	def drawCircle(self, x, y, radius):
		print "API2.circle at %f:%f radius %f" % (x, y, radius)

# Abstraction
class Shape:
	# low-level
	def draw(self):
		pass

	# high-level
	def resizeByPercentage(self, pct):
		pass

# Refined Abstraction
class CircleShape(Shape):
	def __init__(self, x, y, radius, drawingAPI):
		self.__x = x
		self.__y = y
		self.__radius = radius
		self.__drawingAPI = drawingAPI

	# low-level i.e. Implementation specific
	def draw(self):
		self.__drawingAPI.drawCircle(self.__x, self.__y, self.__radius)

	# high-level i.e. Abstraction specific
	def resizeByPercentage(self, pct):
		self.__radius *= pct

def main():
	shapes = [
		CircleShape(1, 2, 3, DrawingAPI1()),
		CircleShape(5, 7, 11, DrawingAPI2())
	]

	for shape in shapes:
		shape.resizeByPercentage(2.5)
		shape.draw()

if __name__ == "__main__":
	main()