possible implementations of casting in c++

Question

I have this snippet of the code in my header :

class A {
private:
    int player;
public:
    A(int initPlayer = 0);
    A(const A&);
    A& operator=(const A&);
    ~A();
    void foo() const;
friend int operator==(const A& i, const A& member) const;
};

implementation of the operator==

int operator==(const A& i, const A& member) const{
    if(i.player == member.player){
        return  1;
    }
    return 0;

}

and I need casting for this part of my code:

i - is some int, which my function receives

A *pa1 = new A(a2);

assert(i == *pa1);

I receive an error non-member function , How can I fix it? thanks in advance

Answer 1

Your error is nothing to do with casting or user-defined conversions.

You can't have a const qualification on a function that isn't a member function so this:

int operator==(const A& i, const A& member) const;

should be this:

int operator==(const A& i, const A& member);

Answer 2

Remove the const qualifier from the friend function. Friend functions are not member functions hence the const qualifier is meaningless.

Answer 3

There are two solutions:

1. Make operator==() a member function, not a friend:

   Interface :

    class A { private: int player; public: A(int initPlayer = 0); A(const A&); A& operator=(const A&); ~A(); void foo() const; int operator==(const A& rhv) const; }; 

   Implementation :

    int A::operator==(const A& rhv) const { return this->player == rhv.player; } 

2. If you really want operator==() as a friend function, just remove the const qualifier, as mentioned in the other posts.