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Thread: Adapter

  1. #1
    Join Date
    Jul 2007
    Posts
    225

    Arrow Adapter

    Hi please see the below code
    Code:
    #include<iostream>
    using namespace std;
    
    class OldRectangle{
            int x1,x2,y1,y2;
            public:
            OldRectangle(int a,int b,int c,int d):x1(a),x2(b),y1(c),y2(d)
            {
                    cout<<"Old Rectangle"<<endl;
            }
            void oldDraw()
            {
                    cout<<"using old drawing method"<<endl;
            }
    };
    
    class Rectangle{
            public:
            virtual void draw()=0;
    };
    
    class RectangleAdapter : public Rectangle, private OldRectangle{
            public:
            RectangleAdapter(int x,int y,int width, int height):
            OldRectangle(x,y,x+width,y+height)
            {
                    cout<<"Initialize the old rectanlge object through this new Rectangle adapter object"<<endl;
            }
            void draw()
            {
                    oldDraw();
            }
    };
    
    int main()
    {
            Rectangle *r= new RectangleAdapter(10,20,33,66);
            r->draw();
            return 0;
    }

    My question is why we need a RectangleAdapter class.
    I can directly write in the main like
    OldRectangle *ptr = new OldRectangle(10,20,10+33,20+66);
    ptr->oldDraw();

    this will do the same thing for me

    Please clarify me.

    Regards

  2. #2
    Join Date
    Jan 2006
    Location
    Singapore
    Posts
    6,196

    Re: Adapter

    Quote Originally Posted by Rajesh1978
    My question is why we need a RectangleAdapter class.
    I can directly write in the main like
    OldRectangle *ptr = new OldRectangle(10,20,10+33,20+66);
    ptr->oldDraw();

    this will do the same thing for me
    But you see, I have written this wonderful function with the prototype:
    Code:
    void beautifulDisplay(Rectangle* rectangle);
    You want to use my function, but OldRectangle has nothing to do with Rectangle. You could derive a new class from Rectangle, but then you have to rewrite stuff that is already implemented in OldRectangle.

    This is where RectangleAdapter comes in: it adapts your existing class' interface to the interface required by my existing function. You do not have to change your class; I do not have to change my function.
    Last edited by laserlight; April 22nd, 2010 at 06:40 AM.
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  3. #3
    Join Date
    Jul 2007
    Posts
    225

    Re: Adapter

    Thanks Laserlight.
    My doubt is clarified.

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