error: conversion from ‘Mstream’ to non-scalar type ‘std::string {aka std::basic_string<char>}’ requested

Question

Could you please help me to resolve the error in the below code.

class Mstream{
     unsigned int len;
     char *str;
};

int main(){
   Mstream m1;
   std::string str=m1;// i see error at this statement
}

error:

conversion from 'Mstream' to non-scalar type 'std::string {aka std::basic_string<char>}' requested

Answer 1

std::string does not have a constructor or operator= that takes an Mstream as input. It does, however, have a constructor that takes a char* and size as input:

int main(){
    Mstream m1;
    std::string str(m1.str, m1.len);
}

Alternatively, you can add a std::string conversion operator to Mstream , then you can assign an Mstream to a std::string :

class Mstream{
    unsigned int len;
    char *str;
    operator std::string() const { return std::string(str, len); }
};

int main(){
    Mstream m1;
    std::string str = m1;
}

Either way, do make sure the Mstream is properly initialized with a valid char* pointer and length value before attempting to do the conversion to std::string .