Operator >> Error

[khal]

Hi I am having a problem with separating my overloaded operator into the .cpp of my class.

main.cpp

#include <iostream>
#include "test.h"
using namespace std;
int main()
{
   test<double> testObject;
   cin >> testObject
    return 0;
}

test.h

#ifndef TEST_H
#define TEST_H
#include <iostream>
using namespace std;

template <class T>
class test
{
    friend istream &operator >>(istream &Input, test<T> &x);
    //If i put the code here it works fine
     public:

     private:
        T ** testArr;

test.cpp

#include <iostream>
#include "test.h"
using namespace std;

template<class T>
 istream &operator >>(istream &userIn, matrix<T> &obj){

}

The Error that I get is
undefined reference to `operator>>(std::istream&, matrix<double>&)'|

[vlad from moscow]

You declared the friend function as a non-template function inside class test however in the cpp file you are declaring it as a template function.

I think that the declaration should look the following way

#ifndef TEST_H
#define TEST_H
#include <iostream>
using namespace std;

template <class T>
class test
{
    template <typename U>
    friend istream & operator >>(istream &, test<U> & );
    //If i put the code here it works fine
     public:

     private:
        T ** testArr;

....

template<class T>
istream & operator >>( istream &userIn, matrix<T> &obj )
{
    return ( userIn );
} 

Also do not forget to place all definitions of the template class in this header.

[khal]

Okay I understand but is it possible to place all the definition inside the test.cpp instead of the header?

[vlad from moscow]

The main shall see the definitions that to generate an instantiation of a template.

[Stewbond]

In english: You need to have template definitions in headers.

[khal]

@Stewbond Thank you lol