Implementing pure virtual functions : virtual function « Class « C++ Tutorial

Home
C++ Tutorial
1.Language Basics
2.Data Types
3.Operators statements
4.Array
5.Development
6.Exceptions
7.Function
8.Structure
9.Class
10.Operator Overloading
11.Pointer
12.File Stream
13.template
14.STL Introduction
15.string
16.vector
17.list
18.bitset
19.set multiset
20.valarray
21.queue stack
22.deque
23.map multimap
24.STL Algorithms Modifying sequence operations
25.STL Algorithms Non modifying sequence operations
26.STL Algorithms Binary search
27.STL Algorithms Sorting
28.STL Algorithms Merge
29.STL Algorithms Min Max
30.STL Algorithms Iterator
31.STL Algorithms Heap
32.STL Algorithms Helper
C / ANSI-C
C Tutorial
C++
Visual C++ .NET
C++ Tutorial » Class » virtual function 
9.28.10.Implementing pure virtual functions
#include <iostream>
 
 class Shape
 {
 public:
     Shape(){}
     virtual ~Shape(){}
     virtual long GetArea() 0
     virtual long GetPerim()0;
     virtual void Draw() 0;
 private:
 };
 
 void Shape::Draw()
 {
     std::cout << "Abstract drawing mechanism!\n";
 }
 
 class Circle : public Shape
 {
 public:
     Circle(int radius):itsRadius(radius){}
     ~Circle(){}
     long GetArea() { return * itsRadius * itsRadius; }
     long GetPerim() { return * itsRadius; }
     void Draw();
 private:
     int itsRadius;
     int itsCircumference;
 };
 
 void Circle::Draw()
 {
     std::cout << "Circle drawing routine here!\n";
     Shape::Draw();
 }
 
 class Rectangle : public Shape
 {
 public:
     Rectangle(int len, int width):
         itsLength(len), itsWidth(width){}
     virtual ~Rectangle(){}
     long GetArea() { return itsLength * itsWidth; }
     long GetPerim() {return 2*itsLength + 2*itsWidth; }
     virtual int GetLength() { return itsLength; }
     virtual int GetWidth() { return itsWidth; }
     void Draw();
 private:
     int itsWidth;
     int itsLength;
 };
 
 void Rectangle::Draw()
 {
     for (int i = 0; i<itsLength; i++)
     {
         for (int j = 0; j<itsWidth; j++)
             std::cout << "x ";
 
         std::cout << "\n";
     }
     Shape::Draw();
 }
 
 class Square : public Rectangle
 {
 public:
     Square(int len);
     Square(int len, int width);
     ~Square(){}
     long GetPerim() {return * GetLength();}
 };
 
 Square::Square(int len):Rectangle(len,len)
 {}
 
 Square::Square(int len, int width):Rectangle(len,width){
     if (GetLength() != GetWidth())
         std::cout << "Error, not a square... a Rectangle??\n";
 }
 
 int main()
 {
     Shape * sp;
 
     sp = new Circle(5);
     sp->Draw();

     sp = new Rectangle(4,6);
     sp->Draw();

     sp = new Square (5);
     sp->Draw();

     return 0;
 }
Circle drawing routine here!
Abstract drawing mechanism!
x x x x x x
x x x x x x
x x x x x x
x x x x x x
Abstract drawing mechanism!
x x x x x
x x x x x
x x x x x
x x x x x
x x x x x
Abstract drawing mechanism!
9.28.virtual function
9.28.1.A virtual function
9.28.2.Access base class's virtual if derived class does not redefine it
9.28.3.Use virtual functions and polymorphism
9.28.4.A pure virtual function
9.28.5.Multiple virtual member functions called in turn
9.28.6.Class with only virtual methods
9.28.7.Use virtual function to calculate area for different shapes
9.28.8.Use Virtual Functions to change the method behaviour
9.28.9.Why Virtual Functions: one interface, multiple methods
9.28.10.Implementing pure virtual functions
www.java2java.com | Contact Us
Copyright 2009 - 12 Demo Source and Support. All rights reserved.
All other trademarks are property of their respective owners.