Getting confused in Virtual calls

[Priya Mishra]

Hi all

if I have the public function in the class which has the key word
virtual i.e

public:
virtual void SetControls();

Then what does this really mean in the program.

Thanks In Advance
Priya

 

[Neelesh Bodas]

Hi all

if I have the public function in the class which has the key word
virtual i.e

public:
virtual void SetControls();

Then what does this really mean in the program.

dynamic binding.
http://www.parashift.com/c++-faq-lite/virtual-functions.html

 

[shan_rish]

Hi all

if I have the public function in the class which has the key word
virtual i.e

public:
virtual void SetControls();

Then what does this really mean in the program.

Thanks In Advance
Priya

The virtual keyword allows you to define an entire different function
with the same name and parameters(arguments) in a derived class. In
your program SetControls can be defined in a derived class with same
signature (same parameters and return values). Please get a good book
and read it.

Cheers
Shan

 

[BigBrian]

The virtual keyword allows you to define an entire different function
with the same name and parameters(arguments) in a derived class.

You can do this without the "virtual" keyword also, but you don't get
dynamic binding.

#include <iostream>

class Base
{
public:
int foo() { std::cout << "in Base::foo()" << std::endl; }
};

class Derived : public Base
{
public:
int foo() { std::cout << "in Derived::foo()" << std::endl; }
};

int main()
{
Base * bp = new Derived();

// no polymorphism because Base::foo() isn't virtual
bp->foo();

return 1;
}

 

[Neil Cerutti]

Hi all

if I have the public function in the class which has the key word
virtual i.e

public:
virtual void SetControls();

Then what does this really mean in the program.

It means that this class provides a function that may vary
polymorphically for its derived classes, in other words, derived
classes may override the function with their own implementation.
In addition, it promises to provide a default implementation that
derived classes can use if they don't want to override it.

 

[BigBrian]

In addition, it promises to provide a default implementation that
derived classes can use if they don't want to override it.

The original post asked what "virtual" means. A member function can be
virtual and still not provide a default implementation.

 

[Neil Cerutti]

The original post asked what "virtual" means. A member
function can be virtual and still not provide a default
implementation.

Yes, but not that specific function. ;-)