conversion from 'std::string' to non-scalar type requested
I have trouble implementing my class. It should be able to initialize from std::string. So I wrote a copy (?) constructor:
CVariable (std::string&, const int p_flags = 0);
I'm trying to make an object of CVariable:
MCXJS::CVariable s_var = (string)"good job";
I'm getting the following error:
F:\Projekty\MCXJS\src\main.cpp|8|error: conversion from 'std::string' to non-scalar type 'MCXJS::CVariable' requested|
How to fix that?
I'M SEARCHING FOR SOLUTION THAT WILL ALLOW SOMETHING EXACTLY AS FOLLOWS:
MCXJS::CVariable s_var = (string)"good job";
Edit: adding (almost) full source code:
cvariable.h
#ifndef CVARIABLE_H
#define CVARIABLE_H
#include <string>
#include <sstream>
namespace MCXJS
{
enum VARTYPE
{
STRING = 0,
INT = 1,
FLOAT = 2
};
class CVariable
{
public:
VARTYPE Type () {return m_type;};
std::string& Value () {return m_value;};
bool SetType (VARTYPE);
private:
const int m_flags;
VARTYPE m_type;
std::string m_value;
// ctors and operators
public:
CVariable (const int p_flags = 0);
CVariable (CVariable&, const int);
CVariable (std::string const&, const int);
CVariable (const int&, const int);
CVariable (const float&, const int);
CVariable& operator= (const CVariable&);
CVariable& operator= (const std::string&);
CVariable& operator= (const int);
CVariable& operator= (const float);
};
};
#endif // CVARIABLE_H
cvariable.cpp
#include "cvariable.h"
using namespace MCXJS;
using namespace std;
CVariable::CVariable (const int p_flags):
m_flags (p_flags)
{};
CVariable::CVariable (CVariable& p_var, const int p_flags = 0):
m_flags (p_flags),
m_type (p_var.Type()),
m_value (p_var.Value())
{};
CVariable::CVariable (std::string const& p_value, const int p_flags = 0):
m_flags (p_flags),
m_type (STRING),
m_value (p_value)
{};
CVariable::CVariable (const int p_value, const int p_flags = 0):
m_flags (p_flags),
m_type (INT)
{
std::ostringstream buffer;
buffer << p_value;
m_value = buffer.str();
};
CVariable::CVariable (const float p_value, const int p_flags = 0):
m_flags (p_flags),
m_type (FLOAT)
{
std::ostringstream buffer;
buffer << p_value;
m_value = buffer.str();
};
main.cpp
#include "cvariable.h"
#include <iostream>
using namespace std;
int main()
{
MCXJS::CVariable s_var = (string)"good job"; // error
cout << s_var.Value() << '\n';
return 0;
}
Edit: adding enum VARPARAM
Edit: OK, solved above, now I have this:
cvariable.cpp|12|error: passing 'const MCXJS::CVariable' as 'this' argument of 'MCXJS::VARTYPE MCXJS::CVariable::Type()' discards qualifiers|
cvariable.cpp|13|error: 开发者_高级运维passing 'const MCXJS::CVariable' as 'this' argument of 'std::string& MCXJS::CVariable::Value()' discards qualifiers|
You need to take this by const reference
CVariable (std::string const&, const int p_flags = 0);
It does not make sense to accept a temporary conversion result by a non-const reference. Changes to that parameter will just be lost afterwards. Making it work by having it be a const reference is easy, so Standard C++ just forbids it.
Have you omitted to add the definition of the '=' operator overload in your code sample? You need to properly define what happens when you assign a string to your object.
MCXJS::CVariable s_var = (string)"good job";
Is it a typo? Should be MCXJS::CVariable s_var = { 0, STRING, std::string("good job") };
or even better, explicitly - MCXJS::CVariable s_var(std::string("good job"), 0);
.
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