Design Patterns Explained C++ Code Examples – Chapter 10: The Bridge Pattern

Design Patterns Explained A New Perspective on Object-Oriented Design (2nd Edition)

by Alan Shalloway and James R. Trott

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Example 10-1

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Example 10-2

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Example 10-3

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Example 10-1

Rectangle

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Rectangle.h

#pragma once

class Rectangle
{
public:
    Rectangle(double, double, double, double);
    virtual void drawLine(double, double, double, double)=0;
    void draw();
public:
    ~Rectangle(void);
private:
    double _x1, _x2, _y1, _y2;
};

Rectangle.cpp

#include "Rectangle.h"

Rectangle::Rectangle(double x1, double y1, double x2, double y2) 
{
    _x1= x1; _y1= y1; _x2= x2; _y2= y2;
}

Rectangle::~Rectangle(void)
{
}

void Rectangle::draw()
{
    drawLine( _x1, _y1, _x2, _y1);
    drawLine( _x2, _y1, _x2, _y2);
    drawLine( _x2, _y2, _x1, _y2);
    drawLine( _x1, _y2, _x1, _y1);
}

V1Rectangle

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V1Rectangle.h

#pragma once
#include "Rectangle.h"

class V1Rectangle : public Rectangle
{
public:
    V1Rectangle(double, double, double, double);
    void drawLine( double, double, double, double);
public:
    ~V1Rectangle(void);
};

V1Rectangle.cpp

#include "V1Rectangle.h"
#include "DP1.h"

V1Rectangle::V1Rectangle(double x1, double y1, double x2, double y2) : 
    Rectangle(x1, y1, x2, y2)
{
}

V1Rectangle::~V1Rectangle(void)
{
}
void V1Rectangle::drawLine( double x1, double y1, double x2, double y2)
{
    DP1::draw_a_line( x1, y1, x2, y2);
}

V2Rectangle

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V2Rectangle.h

#pragma once
#include "Rectangle.h"

class V2Rectangle : public Rectangle
{
public:
    V2Rectangle(double, double, double, double);
    void drawLine( double, double, double, double);
public:
    ~V2Rectangle(void);
};

V2Rectangle.cpp

#include "V2Rectangle.h"
#include "DP2.h"

V2Rectangle::V2Rectangle(double x1, double y1, double x2, double y2) : 
    Rectangle(x1, y1, x2, y2)
{
}

V2Rectangle::~V2Rectangle(void)
{
}
void V2Rectangle::drawLine( double x1, double y1, double x2, double y2)
{
    DP2::drawline( x1, y1, x2, y2);
}

DP1

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DP1.h

#pragma once

class DP1
{
public:
    DP1(void);
    static void draw_a_line( double, double, double, double);
    static void draw_a_circle( double, double, double);
public:
    ~DP1(void);
};

DP1.cpp

#include "DP1.h"

DP1::DP1(void)
{
}

DP1::~DP1(void)
{
}

void DP1::draw_a_line( double x1, double y1, double x2, double y2)
{
    // draw the line
}
void DP1::draw_a_circle( double x, double y, double r)
{
    // draw the circle
}

DP2

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DP2.h

#pragma once

class DP2
{
public:
    DP2(void);
    static void drawline( double, double, double, double);
    static void drawcircle( double, double, double);
public:
    ~DP2(void);
};

DP2.cpp

#include "DP2.h"

DP2::DP2(void)
{
}

DP2::~DP2(void)
{
}

void DP2::drawline( double x1, double x2, double y1, double y2)
{
    // draw the line
}
void DP2::drawcircle( double x, double y, double r)
{
    // draw the circle
}

Example 10-2

Shape

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Shape.h

#pragma once

class Shape
{
public:
    Shape(void);
    virtual void draw()= 0;
public:
    ~Shape(void);
};

Shape.cpp

#include "Shape.h"

Shape::Shape(void)
{
}

Shape::~Shape(void)
{
}

Circle

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Circle.h

#pragma once
#include "Shape.h"

class Circle :
    public Shape
{
public:
    Circle(double, double, double);
    virtual void draw();
    virtual void drawCircle(double, double, double)=0;

public:
    ~Circle(void);
protected:
    double _x, _y, _r;
};

Circle.cpp

#include "Circle.h"

Circle::Circle(double x, double y, double r)
{
    _x= x;
    _y= y;
    _r= r;
}

Circle::~Circle(void)
{
}

void Circle::draw ()
{
    drawCircle( _x, _y, _r);
}

Rectangle

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Rectangle.h

#pragma once
#include "Shape.h"

class Rectangle : public  Shape
{
public:
    Rectangle(double, double, double, double);
    virtual void drawLine(double, double, double, double)=0;
    void draw();
public:
    ~Rectangle(void);
private:
    double _x1, _x2, _y1, _y2;
};

Rectangle.cpp

#include "Rectangle.h"

Rectangle::Rectangle(double x1, double y1, double x2, double y2) 
{
    _x1= x1; _y1= y1; _x2= x2; _y2= y2;
}

Rectangle::~Rectangle(void)
{
}

void Rectangle::draw()
{
    drawLine( _x1, _y1, _x2, _y1);
    drawLine( _x2, _y1, _x2, _y2);
    drawLine( _x2, _y2, _x1, _y2);
    drawLine( _x1, _y2, _x1, _y1);
}

V1Circle

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V1Circle.h

#pragma once
#include "Circle.h"

class V1Circle : public Circle
{
public:
    V1Circle(double, double, double);
    void drawCircle( double, double, double);
public:
    ~V1Circle(void);
};

V1Circle.cpp

#include "V1Circle.h"
#include "DP1.h"

V1Circle::V1Circle(double x, double y, double r) : Circle( x, y, r)
{
}

V1Circle::~V1Circle(void)
{
}

void V1Circle::drawCircle ( double x, double y, double r)
{
    DP1::draw_a_circle( x, y, r);
}

V1Rectangle

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V1Rectangle.h

#pragma once
#include "Rectangle.h"

class V1Rectangle : public Rectangle
{
public:
    V1Rectangle(double, double, double, double);
    void drawLine( double, double, double, double);
public:
    ~V1Rectangle(void);
};

V1Rectangle.cpp

#include "V1Rectangle.h"
#include "DP1.h"

V1Rectangle::V1Rectangle(double x1, double y1, double x2, double y2) : 
    Rectangle(x1, y1, x2, y2)
{
}

V1Rectangle::~V1Rectangle(void)
{
}
void V1Rectangle::drawLine( double x1, double y1, double x2, double y2)
{
    DP1::draw_a_line( x1, y1, x2, y2);
}

V2Circle

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V2Circle.h

#pragma once
#include "Circle.h"

class V2Circle : public Circle
{
public:
    V2Circle(double, double, double);
    void drawCircle( double, double, double);
public:
    ~V2Circle(void);
};

V2Circle.cpp

#include "V2Circle.h"
#include "DP2.h"

V2Circle::V2Circle(double x, double y, double r) : Circle( x, y, r)
{
}

V2Circle::~V2Circle(void)
{
}
void V2Circle::drawCircle ( double x, double y, double r)
{
    DP2::drawcircle( x, y, r);
}

V2Rectangle

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V2Rectangle.h

#pragma once
#include "Rectangle.h"

class V2Rectangle : public Rectangle
{
public:
    V2Rectangle(double, double, double, double);
    void drawLine( double, double, double, double);
public:
    ~V2Rectangle(void);
};

V2Rectangle.cpp

#include "V2Rectangle.h"
#include "DP2.h"

V2Rectangle::V2Rectangle(double x1, double y1, double x2, double y2) : 
    Rectangle(x1, y1, x2, y2)
{
}

V2Rectangle::~V2Rectangle(void)
{
}
void V2Rectangle::drawLine( double x1, double y1, double x2, double y2)
{
    DP2::drawline( x1, y1, x2, y2);
}

DP1

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DP1.h

#pragma once

class DP1
{
public:
    DP1(void);
    static void draw_a_line( double, double, double, double);
    static void draw_a_circle( double, double, double);
public:
    ~DP1(void);
};

DP1.cpp

#include "DP1.h"

DP1::DP1(void)
{
}

DP1::~DP1(void)
{
}

void DP1::draw_a_line( double x1, double y1, double x2, double y2)
{
    // draw the line
}
void DP1::draw_a_circle( double x, double y, double r)
{
    // draw the circle
}

DP2

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DP2.h

#pragma once

class DP2
{
public:
    DP2(void);
    static void drawline( double, double, double, double);
    static void drawcircle( double, double, double);
public:
    ~DP2(void);
};

DP2.cpp

#include "DP2.h"

DP2::DP2(void)
{
}

DP2::~DP2(void)
{
}

void DP2::drawline( double x1, double x2, double y1, double y2)
{
    // draw the line
}
void DP2::drawcircle( double x, double y, double r)
{
    // draw the circle
}

Example 10-3

Client

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Client.h

#pragma once

class Client
{
public:
    Client(void);
public:
    ~Client(void);
};

Client.cpp

#include "Client.h"
#include "Shape.h"
#include "Factory.h"

Client::Client(void)
{
}

Client::~Client(void)
{
}

void static main ()
{
    Shape **myShapes;
    Factory myFactory;

    // get Rectangles from some other source
    myShapes= myFactory.getShapes();
    for (int i= 0; i < sizeof(myShapes)/ sizeof(myShapes[0]); i++)
        myShapes[i]->draw();
}

Factory

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Factory.h

#pragma once

#include "Shape.h"
#include "Circle.h"
#include "Rectangle.h"
#include "Drawing.h"
#include "V1Drawing.h"
#include "V2Drawing.h"

class Factory
{
public:
    Factory(void);
    ~Factory(void);
    Shape** getShapes();
};

Factory.cpp

#include "Factory.h"

Factory::Factory(void)
{
}

Factory::~Factory(void)
{
}

Shape** Factory::getShapes ()
{
    Shape **myShapes;
    // Figure out the shapes needed.
    // create them and put them in the array myShapes
    return myShapes;
}

Shape

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Shape.h

#pragma once
#include "Drawing.h"

class Shape
{
public:
    Shape(Drawing *aDrawing);
    virtual void draw()= 0;

protected:
    Drawing *myDrawing;
    void drawLine( double, double, double, double);
    void drawCircle( double, double, double);

public:
    ~Shape(void);
};

Shape.cpp

#include "Shape.h"

Shape::Shape(Drawing *aDrawing)
{
    myDrawing= aDrawing;
}

Shape::~Shape(void)
{
}

void Shape::drawLine( double x1,double y1, double x2,double y2) 
{
   myDrawing->drawLine(x1,y1,x2,y2);
}

void Shape::drawCircle( double x,double y,double r) 
{
   myDrawing->drawCircle(x,y,r);
}

Circle

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Circle.h

#pragma once
#include "Shape.h"

class Circle : public Shape
{
public:
    Circle(Drawing*, double, double, double);
    virtual void draw();
    virtual void drawCircle(double, double, double)=0;

public:
    ~Circle(void);
protected:
    double _x, _y, _r;
};

Circle.cpp

#include "Circle.h"
#include "Factory.h"

Circle::Circle(Drawing *aDrawing, double x, double y, double r) : Shape (aDrawing)
{
    _x= x;
    _y= y;
    _r= r;
}

Circle::~Circle(void)
{
}

void Circle::draw ()
{
    drawCircle( _x, _y, _r);
}

Rectangle

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Rectangle.h

#pragma once
#include "Shape.h"

class Rectangle : public  Shape
{
public:
    Rectangle(Drawing*, double, double, double, double);
    virtual void drawLine(double, double, double, double)=0;
    void draw();
public:
    ~Rectangle(void);
private:
    double _x1, _x2, _y1, _y2;
};

Rectangle.cpp

#include "Rectangle.h"

Rectangle::Rectangle(Drawing *aDrawing, double x1, double y1, double x2, double y2) : 
    Shape (aDrawing)
{
    _x1= x1; _y1= y1; _x2= x2; _y2= y2;
}

Rectangle::~Rectangle(void)
{
}

void Rectangle::draw()
{
    drawLine( _x1, _y1, _x2, _y1);
    drawLine( _x2, _y1, _x2, _y2);
    drawLine( _x2, _y2, _x1, _y2);
    drawLine( _x1, _y2, _x1, _y1);
}

Drawing

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Drawing.h

#pragma once

class Drawing
{
public:
    Drawing(void);
public:
    ~Drawing(void);
    virtual void drawLine( double, double, double, double)=0;
    virtual void drawCircle( double, double, double)=0;
};

Drawing.cpp

#include "Drawing.h"

Drawing::Drawing(void)
{
}

Drawing::~Drawing(void)
{
}

V1Drawing

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V1Drawing.h

#pragma once
#include "drawing.h"
#include "DP1.h"

class V1Drawing : public Drawing
{
public:
    V1Drawing(void);
public:
    ~V1Drawing(void);
    void drawLine( double, double, double, double);
    void drawCircle( double, double, double);
private:
    DP1 myDP1;
};

V1Drawing.cpp

#include "V1Drawing.h"

V1Drawing::V1Drawing(void)
{
}

V1Drawing::~V1Drawing(void)
{
}

void V1Drawing::drawLine ( double x1,double y1, double x2,double y2) 
{
   DP1::draw_a_line(x1,y1,x2,y2);
}

void V1Drawing::drawCircle (double x,double y,double r) 
{
   DP1::draw_a_circle(x,y,r);
}

V2Drawing

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V2Drawing.h

#pragma once
#include "drawing.h"
#include "DP2.h"

class V2Drawing : public Drawing
{
public:
    V2Drawing(void);
public:
    ~V2Drawing(void);
    void drawLine( double, double, double, double);
    void drawCircle( double, double, double);
private:
    DP2 myDP2;
};

V2Drawing.cpp

#include "V2Drawing.h"

V2Drawing::V2Drawing(void)
{
}

V2Drawing::~V2Drawing(void)
{
}

void V2Drawing::drawLine (double x1,double y1, double x2,double y2) 
{
   // arguments are different in DP2
   // and must be rearranged
   DP2::drawline(x1,x2,y1,y2);
}

void V2Drawing::drawCircle ( double x, double y,double r) 
{
   DP2::drawcircle(x,y,r);
}

DP1

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DP1.h

#pragma once

class DP1
{
public:
    DP1(void);
    static void draw_a_line( double, double, double, double);
    static void draw_a_circle( double, double, double);
public:
    ~DP1(void);
};

DP1.cpp

#include "DP1.h"

DP1::DP1(void)
{
}

DP1::~DP1(void)
{
}

void DP1::draw_a_line( double x1, double y1, double x2, double y2)
{
    // draw the line
}
void DP1::draw_a_circle( double x, double y, double r)
{
    // draw the circle
}

DP2

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DP2.h

#pragma once
#include "DP2.h"

class DP2
{
public:
    DP2(void);
    static void drawline( double, double, double, double);
    static void drawcircle( double, double, double);
public:
    ~DP2(void);
};

DP2.cpp

#include "DP2.h"

DP2::DP2(void)
{
}

DP2::~DP2(void)
{
}

void DP2::drawline( double x1, double x2, double y1, double y2)
{
    // draw the line
}
void DP2::drawcircle( double x, double y, double r)
{
    // draw the circle
}