Stringstream - Convert an object to a string

Question

I have a complex object that I want to be able to pass into a std::ostringstream with the << operator just like a string or int. I want to give the ostringstream the object's unique id (int) and/or name (string). Is there an operator or method I can implement in my class to allow this to work?

Yes just overload the << operator - see http://stackoverflow.com/questions/4421706/operator-overloading — Martin Beckett, Jun 05 '12 at 22:01
unique id in what context? In an instance of running process you could use it's memory address. — Ivarpoiss, Jun 05 '12 at 22:02
They are "Student" objects, for a class project. Each Student object has a name, id, address, and phone number, and are built from a txt file. — Martin, Jun 05 '12 at 22:09
@MartinBeckett - overload << for my class, or for `ostringstream`? — Martin, Jun 05 '12 at 22:10
@mouseas - for your class. Each class simply has a function that is called when you ask for '< — Martin Beckett, Jun 05 '12 at 22:11

score 4 · Accepted Answer · answered Jun 05 '12 at 23:29

Define an operator overload in the same namespace as your class:

template<typename charT, typename traits>
std::basic_ostream<charT, traits> &
operator<< (std::basic_ostream<charT, traits> &lhs, Your_class const &rhs) {
    return lhs << rhs.id() << ' ' << rhs.name();
}

If the output function needs access to private members of your class then you can define it as a friend function:

class Your_class {
    int id;
    string name;

    template<typename charT, typename traits>
    friend std::basic_ostream<charT, traits> &
    operator<< (std::basic_ostream<charT, traits> &lhs, Your_class const &rhs) {
        return lhs << rhs.id << ' ' << rhs.name;
    }
};

Note that this does not result in a member function, it's just a convenient way to declare and define a friend function at once.

The `traits` template parameter has a default value, so it can be skipped. — AlwaysLearning, Dec 09 '15 at 11:51

Stringstream - Convert an object to a string

1 Answers1