Example of C + + virtual function usage

PROGRAM1:
Class a{

Public

void print () {cout<< "This is A" <<ENDL;}

};

Class B:public a{

Public

void print () {cout<< "This is B" <<ENDL;}

};

int main () {  

A;

b b;

A.print ();

B.print ();

}

Output:

This is A
This is B

PROGRAM2:

int main () {   //main2

A;

b b;

A * p1=&a;

A * p2=&b;

P1->print ();

P2->print ();

}

Output:

This is A

This is A

PROGRAM3:

Class a{

Public

virtual void print () {cout<< "This is A" <<ENDL;}  Now it's a virtual function.

};

Class B:public a{

Public

void print () {cout<< "This is B" <<ENDL;}  Do you need to add the keyword virtual to the front?

};

Output:

This is A
This is B



Dry:

If the child class overrides the virtual function of the parent class
A pointer to the parent class, or a reference to an object that actually points to the child class
When a virtual function is called through the pointer or reference, the (virtual) function of the subclass is called

If it is not a virtual function, the function of the parent class will be called

Example of C + + virtual function usage