c++ - What is wrong with my operator<< overload code? -

i trying overload <<-operator class can use std::cout it. i've copied code found online this, can't work.
error says:

error c2662: 'nspace::elementcopy::name' : cannot convert 'this' pointer  'const nspace::elementcopy' 'nspace::elementcopy &' 

the error in <<-operator implementation: (see code comment)

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here header file, elementcopy.h:

#pragma once #include <string> #include <iostream>  namespace nspace {     class elementcopy     {         public:             std::string name();     };      std::ostream& operator<< (std::ostream& stream, const elementcopy& arg)     {         stream << arg.name(); //compiler error @ line         return stream;     } } 

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and here short code file, elementcopy.cpp:

#include "elementcopy.h"  namespace nspace {     std::string elementcopy::name()     {         return "string";     } } 

i can't figure out error. why getting it? operator overload doesn't have "this" speak of. how can fix this?

you want make name() method const:

class elementcopy {     public:         std::string name() const; }; 

this way, allowed call on const reference in operator<<