Thread: iostream overloaded operators

The stream operators are designed from the get go to operate on the built in types: int, char, float, etc... For example:

Code:

int foo;
cin >> foo;  // Read from cin stream into an integer

float bar = 12.9f;
cout << bar; // Write to cout stream converting from a float

Overloading these operators allows you to extend this capability to user defined types (custom class/struct objects).

Code:

#include <string>
#include <iostream>
using namespace std;

struct person
{
    string first_name;
    string last_name;
    int age;
    person() {}
    person(const string& fname, const string& lname, int yrs) : first_name(fname), last_name(lname), age(yrs) {}
};

// Overloaded stream extraction operator
istream& operator>>(istream& is, person& per)
{
    return is >> per.first_name >> per.last_name >> per.age;
}

// Overloaded stream insertion operator
ostream& operator<<(ostream& os, const person& per)
{
    return os << "First Name: " << per.first_name << "\nLast Name : " << per.last_name
              << "\nAge       : " << per.age;
}

int main()
{
    person h_simpson("Homer","Simpson",40);

    //Output to cout using overloaded stream insertion operator<< for custom object of type person
    cout << h_simpson << endl;

    person temp;
    // Read from cin using overloaded stream extraction operator>> for custom object of type person
    cin >> temp;

    cout << temp << endl;

    return 0;
}

Example I/O:

Code:

First Name: Homer
Last Name : Simpson
Age       : 40
Marge Simpson 38
First Name: Marge
Last Name : Simpson
Age       : 38