Cpp - Classes with Other Classes as Member Data

Introduction

You can build a complex class by declaring simpler classes and including them in?the declaration of the more complicated class.

The following code creates a rectangle class which is composed of four lines.

Each line is defined by two points.

A point is defined by x and y coordinates.

Demo

#include <iostream> 
 
class Point //from w w w.ja  va2 s.  c  om
{ 
    // no constructor, use default 
public: 
    void setX(int newX) { x = newX; } 
    void setY(int newY) { y = newY; } 
    int getX() const { return x; } 
    int getY() const { return y; } 
private: 
    int x; 
    int y; 
}; 
 
class  Rectangle 
{ 
public: 
    Rectangle(int newTop, int newLeft, int newBottom, int newRight); 
    ~Rectangle() {} 
 
    int getTop() const { return top; } 
    int getLeft() const { return left; } 
    int getBottom() const { return bottom; } 
    int getRight() const { return right; } 
 
    Point getUpperLeft() const { return upperLeft; } 
    Point getLowerLeft() const { return lowerLeft; } 
    Point getUpperRight() const { return upperRight; } 
    Point getLowerRight() const { return lowerRight; } 
 
    void setUpperLeft(Point location); 
    void setLowerLeft(Point location); 
    void setUpperRight(Point location); 
    void setLowerRight(Point location); 
 
    void setTop(int newTop); 
    void setLeft (int newLeft); 
    void setBottom (int newBottom); 
    void setRight (int newRight); 
 
    int getArea() const; 
 
private: 
    Point upperLeft; 
    Point upperRight; 
    Point lowerLeft; 
    Point lowerRight; 
    int top; 
    int left; 
    int bottom; 
    int right; 
};  
Rectangle::Rectangle(int newTop, int newLeft, int newBottom, int newRight) 
{ 
    top = newTop; 
    left = newLeft; 
    bottom = newBottom; 
    right = newRight; 
 
    upperLeft.setX(left); 
    upperLeft.setY(top); 
 
    upperRight.setX(right); 
    upperRight.setY(top); 
 
    lowerLeft.setX(left); 
    lowerLeft.setY(bottom); 
 
    lowerRight.setX(right); 
    lowerRight.setY(bottom); 
} 
 
void Rectangle::setUpperLeft(Point location) 
{ 
    upperLeft = location;  
    upperRight.setY(location.getY()); 
    lowerLeft.setX(location.getX()); 
    top = location.getY(); 
    left = location.getX(); 
} 
 
void Rectangle::setLowerLeft(Point location) 
{ 
    lowerLeft = location;  
    lowerRight.setY(location.getY()); 
    upperLeft.setX(location.getX()); 
    bottom = location.getY(); 
    left = location.getX(); 
} 
 
void Rectangle::setLowerRight(Point location) 
{ 
    lowerRight = location;  
    lowerLeft.setY(location.getY()); 
    upperRight.setX(location.getX()); 
    bottom = location.getY(); 
    right = location.getX(); 
} 
 
void Rectangle::setUpperRight(Point location) 
{ 
    upperRight = location;  
    upperLeft.setY(location.getY()); 
    lowerRight.setX(location.getX()); 
    top = location.getY(); 
    right = location.getX(); 
} 
   
void Rectangle::setTop(int newTop) 
{ 
    top = newTop; 
    upperLeft.setY(top); 
    upperRight.setY(top); 
} 
 
void Rectangle::setLeft(int newLeft) 
{ 
    left = newLeft; 
    upperLeft.setX(left); 
    lowerLeft.setX(left); 
} 
 
void Rectangle::setBottom(int newBottom) 
{ 
    bottom = newBottom; 
    lowerLeft.setY(bottom); 
    lowerRight.setY(bottom); 
} 
 
void Rectangle::setRight(int newRight) 
{ 
    right = newRight; 
    upperRight.setX(right); 
    lowerRight.setX(right); 
} 
 
int Rectangle::getArea() const 
{ 
    int width = right - left; 
    int height = top - bottom; 
    return (width * height); 
} 
 
int main() 
{ 
    // initialize a local Rectangle variable 
    Rectangle myRectangle(100, 20, 50, 80); 
 
    int area = myRectangle.getArea(); 
 
    std::cout << "Area: " << area << std::endl; 
    std::cout << "Upper Left X Coordinate: "; 
    std::cout << myRectangle.getUpperLeft().getX() << std::endl; 
    return 0; 
}

Result

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