Question

Which operator do I have to overload if I want to use sth like this?

MyClass C;

cout<< C;

The output of my class would be string.

Answer 1

if you’ve to overload operator<< as:

std::ostream& operator<<(std::ostream& out, const MyClass & obj)
{
   //use out to print members of obj, or whatever you want to print
   return out;
}

If this function needs to access private members of MyClass, then you’ve to make it friend of MyClass, or alternatively, you can delegate the work to some public function of the class.

For example, suppose you’ve a point class defined as:

struct point
{
    double x;
    double y;
    double z;
};

Then you can overload operator<< as:

std::ostream& operator<<(std::ostream& out, const point & pt)
{
   out << "{" << pt.x <<"," << pt.y <<"," << pt.z << "}";
   return out;
}

And you can use it as:

point p1 = {10,20,30};
std::cout << p1 << std::endl;

Output:

{10,20,30}

Online demo : http://ideone.com/zjcYd

Hope that helps.