Abstract classes are the classes which contains one or more abstract method; and abstract methods are the methods which does not contain any implementation,

but the child-class need to implement these methods otherwise error will be reported. In this way, we can force the child-class to implement certain methods in it.

We can define, abstract classes and abstract method using keyword ‘virtual void’, as shown in Line 27

Since, ‘scarySound’ is defined as abstract method at Line 27, therefore it is compulsory to implement it in all the subclasses.

Note

// abstractClassEx.cpp

#include <iostream>

using namespace std;

class Jungle{

private: // not accessible outside the class

string visitorName;

public: // to allow access to function 'welcomeMessage' outside the class

// setVisitorName is accessible outside the class, which will set the visitor name

void setVisitorName(string name){

visitorName = name;

}

// function to retrieve the visitorName as it is not accessible directly

string getVisitorName(){

return visitorName;

}

// welcome message

void welcomeMessage(){

cout << "Welcome to Jungle " << getVisitorName();

}

virtual void scarySound() = 0;

};

class Animal : public Jungle{

public:

void scarySound(){

cout << "Animals are running away due to scary sound." << endl;

}

};

class Bird : public Jungle{

public:

void scarySound(){

cout << "Birds are flying away due to scary sound." << endl;

}

};

// Now, it is compulsory to define 'scarySound' in Insect as well

class Insect : public Jungle{

public:

void scarySound(){

cout << "Insects do not care about scary sound." << endl;

}

};

int main(){

Animal a;

Bird b;

Insect i;

a.scarySound();

b.scarySound();

i.scarySound();

return 0;

}

/* Outputs

Animals are running away due to scary sound.

Birds are flying away due to scary sound.

Insects do not care about scary sound.

*/