Abstract classes are the way to achieve abstraction in C++. Abstraction in C++ is the process to hide the internal details and showing functionality only. Abstraction can be achieved by two ways:
Abstract class and interface both can have abstract methods which are necessary for abstraction.
In C++ class is made abstract by declaring at least one of its functions as <>strong>pure virtual function. A pure virtual function is specified by placing "= 0" in its declaration. Its implementation must be provided by derived classes.
Let's see an example of abstract class in C++ which has one abstract method draw(). Its implementation is provided by derived classes: Rectangle and Circle. Both classes have different implementation.
#include <iostream>
using namespace std;
class Shape
{
public:
virtual void draw()=0;
};
class Rectangle : Shape
{
public:
void draw()
{
cout < <"drawing rectangle..." < <endl;
}
};
class Circle : Shape
{
public:
void draw()
{
cout <<"drawing circle..." < <endl;
}
};
int main( ) {
Rectangle rec;
Circle cir;
rec.draw();
cir.draw();
return 0;
}
