A pure virtual function : 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 
9.28.4.A pure virtual function
#include <iostream> 
#include <cstring> 
using namespace std; 
 
class Shape 
  double width; 
  double height; 
 
  char name[20]
public
 
  Shape() { 
    width = height = 0.0
    strcpy(name, "unknown")
  
 
  Shape(double w, double h, char *n) { 
    width = w; 
    height = h; 
    strcpy(name, n)
  
 
  Shape(double x, char *n) { 
    width = height = x; 
    strcpy(name, n)
  
 
  void display() { 
    cout << "Width and height are " << width << " and " << height << "\n"
  
 
  double getWidth() { return width; 
  double getHeight() { return height; 
  void setWidth(double w) { width = w; 
  void setHeight(double h) { height = h; 
  char *getName() { return name; 
 
  virtual double area() 0
 
}
 
class Triangle : public Shape 
  char style[20];
public
 
  Triangle() { 
    strcpy(style, "unknown")
  
 
  Triangle(char *str, double w, double h: Shape(w, h, "triangle") { 
    strcpy(style, str)
  
   
  Triangle(double x: Shape(x, "triangle") { 
    strcpy(style, "isosceles");  
  
 
  double area() { 
    return getWidth() * getHeight() 2
  
 
  void showStyle() { 
    cout << "Triangle is " << style << "\n"
  
}
 
class Rectangle : public Shape 
public
 
  Rectangle(double w, double h: Shape(w, h, "rectangle") { }  
  
  Rectangle(double x: Shape(x, "rectangle") { }  
 
  bool isSquare() { 
    if(getWidth() == getHeight()) 
       return true
    return false
  
 
  double area() { 
    return getWidth() * getHeight()
  
}
 
int main() { 
  Shape *shapes[4]
  
  shapes[0= &Triangle("right"8.012.0);  
  shapes[1= &Rectangle(10);  
  shapes[2= &Rectangle(104);  
  shapes[3= &Triangle(7.0);  
  
  for(int i=0; i < 4; i++) {  
    cout << "object is " << shapes[i]->getName() << "\n";  
    cout << "Area is " << shapes[i]->area() << "\n\n";  
  }  
 
  return 0
}
object is triangle
Area is 24.5

object is triangle
Area is 24.5

object is triangle
Area is 24.5

object is triangle
Area is 24.5
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.