I have a class employee
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
class employee
{
public:
double operator + (employee);
istream& operator>> (istream&);
employee(int);
double getSalary();
private:
double salary;
};
int main()
{
employee A(400);
employee B(800);
employee C(220);
cin>>C;
}
employee::employee(int salary)
{
this->salary = salary;
}
double employee::operator + (employee e)
{
double total;
total = e.salary + this->salary;
return total;
}
double employee::getSalary()
{
return this->salary;
}
istream& employee::operator>> (istream& in)
{
in>>this->salary;
return in;
}
I am trying to overload the input operator >> to read in the employee object but i am getting the following error
no match for operator >> in std::cin
What am i doing wrong ???
edit: I know how to do it through a friend function , i am now trying to learn how to do it through a member function
I know how to do it through a friend function , i am now trying to learn how to do it through a member function
You can't.
For a binary operator@ and objects A a and B b, the syntax a @ b will call either a non-member function of the form operator@(A,B) or a member function of the form A::operator@(B). Nothing else.
So to make std::cin >> C work it must be as a member of std::istream, but since you can't modify std::istream you can't implement operator>> as a member function.
(Unless you want to be weird and unconventional and write C << std::cin or C >> std::cin, but if you do that other programmers will hate you for being confusing and unconventional. Do not do this.)
You need to declare it thusly:
class employee
{
public:
friend std::istream& operator >> (std::istream& is, employee& employee);
}; // eo class employee
Implementation:
std::istream& employee::operator >> (std::istream& is, employee& employee)
{
is >> employee.salary; // this function is a friend, private members are visible.
return is;
};
As a side note, it's generally a bad idea to do using namespace std; within a header file.
It seems that we cannot declare operator << inside class declaration. I've tried it and it is OK.
#include <stdio.h>
#include <iostream>
using namespace std;
struct foo {
int field;
};
istream& operator >> (istream& cin, foo& a){
cin >> a.field;
return cin;
}
foo a;
main(){
cin >> a;
}
