warning assignment operator class reference - c++

Question

i have this code:
class ABC{
public:
ABC(std::ostream& os) : _os(os) {}
void operator() (const Stud* course) {
Stud->print(_os);
}
ABC& operator=(const ABC& other); //Declaration of operator=
private:
std::ostream& _os;
};
befor i define assignment operator i get warning "assignment operator could not be generated".
i want assignment between object this class do nothing, its just class print in for_each algorithm.
i try write :
ABC& operator=(const ABC& other){
return *this;
}
but still get warning the other not use.
how can i define assignment operator do nothing. (no Use the #pragma warning statement to suppress the warning).
thanks!

Answer 1

To get rid of the warning about an unused argument, just don't name it:
ABC& operator=(const ABC&){
return *this;
}
The reason that the compiler can't generate an assignment operator for your class is that it has a reference variable, and these can only be initialised, never re-assigned.
If you don't need an assignment operator, but only added one to make the compiler happy, you can declare it private and then not provide an implementation.

Answer 2

Few problems in your code...
class ABC
{
public:
ABC(std::ostream& os) : _os(os) {}
void operator() (const Stud* course)
{
//Stud->print(_os); // you can't use Stud here - this is wrong
course->print(_os);
}
ABC& operator=(const ABC& other); //Declaration of operator=
private:
std::ostream& _os;
};
Additionally, as operator() defines course as const Stud* the print method in Stud class should be defined as const as well.
other than that, the code compiles perfercly.