how do i operator overload <<?

[trumpler]

it is said that the it must receive 2 parameters.
1)istream reference(e.g cin)//receives value from cin

2)object reference//to put the values received from cin into the specific object

the error say that the function must take exactly one argument.
so how do I solve this?

 #include <iostream>
#include <string>
#include "add.h"
#include "m.h"
#include <fstream>
using namespace std;


class opoverload{
public:
    int x,y;

    istream& operator>>(istream &a,opoverload &obj){
    a>>obj.x;
    return a;
    }

};



int main()
{


}

[keskiverto]

That operator cannot be a member function. It has to be a standalone function.

[coder777]

Line 13: Put a friend in front of the function:

    friend istream& operator>>(istream &a,opoverload &obj){
    a>>obj.x;
    return a;
    }

This actually makes the function standalone (as keskiverto mentioned).

[icy1]

@coder777 Interesting. Usually I've seen the friendship just declared but the definition outside the class' curly braces, but I guess you could implement right then and there too (as long as you realize it's not a member function).

@trumpler Check the function signature -- you should return the stream.

#include <iostream>
#include <vector>
#include <sstream>

using namespace std;

class Cell
{
public:
    Cell() {}
    Cell(int x, int y) : x(x), y(y) {} // Useful but unused

    friend ostream& operator<<(ostream& os, const Cell& c)
    {
        os << "(" << c.x << ", " << c.y << ")";
        return os;
    }
    friend istream& operator>>(istream& is, Cell& c)
    {
        is >> c.x >> c.y;
        return is;
    }

private:
    int x;
    int y;
};

int main() 
{
    const char* data_text = R"LITERAL(4 5
12 -3
0 2
19 34
)LITERAL";

    // Imitate file stream
    istringstream iss(data_text);
    
    // Parsing
    vector<Cell> cells;
    Cell tmp;
    while(iss >> tmp)
        cells.emplace_back(tmp);
    
    // Checking data
    cout << "Cells found:\n";
    for (const Cell& c : cells)
        cout << c << '\n';

    return 0;
}

Cells found:
(4, 5)
(12, -3)
(0, 2)
(19, 34)