2 questions--virtual operators and operator=

[c++novice]

1--Can operators be virtual?
2--What is the difference between an operator= returning a refernce Vs a value?

[velthuijsen]

Might want to take a look at http://www.parashift.com/c++-faq-lite

#include <iostream>

using namespace std;

class A {
public:
A() {
this->Foo();
This is not needed, the this-> is implictly added. And you might want
to read Might want to take a look at
http://www.parashift.com/c++-faq-lite ,
10.7 in the FAQ about the dangers of using this in the constructor (no
danger in this case though).
}
virtual void Foo() {
cout << "A::Foo()" << endl;
}
virtual A& operator=(const A &rhs){
cout << "A& operator=(const A&)" << endl;
if(this == &rhs)
return *this;
return *this;

Why bother with a selfassignment check if you don't do anything with
the result?
}
// virtual A &operator++( );
};

class B : public A {
public:
B() {
this->Foo();
}
virtual void Foo() { cout << "B::Foo()" << endl;
}
virtual B& operator=(const B &rhs){
cout << "B& operator=(const B&)" << endl;
if(this == &rhs)
return *this;
return *this;
} // virtual B &operator++( );
};

int main(int, char**)
please use int main () if you are not planning on using the command
line args {
A objA;
B objB;
objA = objB;
if you ever want to do this it is better to write
A* objA = new B;
Do not forget to call delete when you don't need objA anymore or it
will result in memory loss
or write
B objB;
A* objA = &objB;
The danger is here that you can call delete on objA releasing the
memory that objB points to. Meaning that if you try to use objB from
that point on your program should crash.

Doing this will result in the virtual functions you have overridden to
be accessed.
if you write
B objB;
A* objA = &objB;
objA->Foo();
it will put to the screen B::Foo()

Another point is that doing
A objA;
B objB;
objA = objB;
will result in slicing. Which means losing anything that the derived
class added to the base class in the form of datamembers and
functions.


B anotherobjB;
anotherobjB = objA;
This line should have generated an error. The compiler should complain
that B doesn't have any operator= overloads that accept a right side
of class A.
Class B might be a class A but class A is not a class B. You need to
explicitly specify a return 0;
}
how can we call op= of class B?
but op= if not declared, generated by compiler for every class then
why virtual it.

You need to explictly define
virtual B& operator=(const A &rhs)
{
// do stuff
}

if that isn't the answer on your question please explain what you want
more verbose please.

[c++novice]

ve*********@hot mail.com (velthuijsen) wrote in message news:<e5******* *************** ****@posting.go ogle.com>...

Might want to take a look at http://www.parashift.com/c++-faq-lite

Thank u and u too john.
I am clear now on this.

[c++novice]

ve*********@hot mail.com (velthuijsen) wrote in message news:<e5******* *************** ****@posting.go ogle.com>...

Might want to take a look at http://www.parashift.com/c++-faq-lite

Thank u and u too john.
I am clear now on this.