Как сделать преобразование в string для своего класса

Var a = "dfsfdfd";
string b = (string)a;

Var::operator string ()

Var::operator string ()
{
    string ttemp;
    if(this->num !=INT_MIN){
        ttemp = to_string(static_cast<long long>(this->num));
    }else if(this->dnum !=DBL_MIN){
        ttemp = to_string(static_cast<long double>(this->dnum));
    }else{
        wchar_t * temp = (wchar_t*)this->str.c_str();
        char ch[4];
        for (int i = 0; i < this->str.length(); i++)
        {
            wcstombs(ch,&temp[i],1);
            ttemp += ch[0];
        }
    }
    return ttemp;
}

    operator string ();
    operator char* ();

#include <iostream>
#include <string>
using namespace std;
class test
{
public:
    operator string()
    {
        return "Hello world";
    }
    operator char* ()
    {
        return "Hello world";
    }
};
 
int main(int argc, char* argv[])
{
    test tmp;
    auto ss = (string)tmp;
    cout << ss;
    system("pause");
    return 0;
}

delete[]temp;

C:\Program Files\CodeBlocks\project\temp\main.cpp||In function 'int main(int, char**)':|
C:\Program Files\CodeBlocks\project\temp\main.cpp|2014|error: call of overloaded 'basic_string(Var&)' is ambiguous|
C:\Program Files\CodeBlocks\project\temp\main.cpp|2014|note: candidates are:|
C:\MinGWx86\i686-w64-mingw32\include\c++\bits\basic_string.h|512|note: std::basic_string<_CharT, _Traits, _Alloc>::basic_string(std::basic_string<_CharT, _Traits, _Alloc>&&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]|
C:\MinGWx86\i686-w64-mingw32\include\c++\bits\basic_string.h|495|note: std::basic_string<_CharT, _Traits, _Alloc>::basic_string(const _CharT*, const _Alloc&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]|
C:\MinGWx86\i686-w64-mingw32\include\c++\bits\basic_string.h|460|note: std::basic_string<_CharT, _Traits, _Alloc>::basic_string(const std::basic_string<_CharT, _Traits, _Alloc>&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]|
||=== Build finished: 1 errors, 15 warnings (0 minutes, 1 seconds) ===|

class Var {
private:
    string data;
public:
    Var(string data) {
        this->data = data;
    }
 
    operator string() const {
        return data;
    }
 
    operator const char*() const {
        return data.c_str();
    }
};
 
void main() {
    const Var var = "Some text";
    cout << var; // Вывод: Some text
 
    _getch();
}

class Var {
void method(const Var& other) const {
 
}
};