WritePrivateProfileString works in main but not in function - c++

Question

I am trying to use WritePrivateProfileString and GetPrivateProfileInt for a .ini parser.
When I put the code below into main(), or into a class constructor, it works for writing and reading.
But, when I make functions for writing and reading, and call the functions in main(), nothing happens, although the functions are run as they will cout something if I ask them to.
Here is the test program I wrote to demonstrate this:
#include <iostream>
#include <Windows.h>
#include <fstream>
#include <string>
#define CStringify(x) std::to_string(x).c_str()
int testvar = 12;
int returntestvar = 0;
std::fstream config;
std::string configstring = ".//config.ini";
int main()
{
WriteINI();
ReadINI();
std::cout << returntestvar << std::endl;
getchar();
}
void WriteINI()
{
config.open("config.ini", std::ios::app);
WritePrivateProfileString("Test", "Test1", CStringify(testvar), configstring.c_str());
}
void ReadINI()
{
config.open("config.ini", std::ios::app);
returntestvar = GetPrivateProfileInt("Test", "Test1", 0, configstring.c_str());
}
The above code creates and then edits an .ini file, as it is expected to.
However, if I move the code into a class, it will no longer work.
main.cpp
#include <iostream>
#include <Windows.h>
#include <fstream>
#include <string>
#include "INIClassTest.h"
extern INIParser* Parse;
int main()
{
Parse->WriteINI();
Parse->ReadINI();
std::cout << Parse->returntestvar << std::endl;
getchar();
}
INIClassTest.h
#pragma once
#include <fstream>
#include <string>
#include <Windows.h>
#define CStringify(x) std::to_string(x).c_str()
class INIParser
{
public:
INIParser();
void WriteINI();
void ReadINI();
int testvar;
int returntestvar;
std::fstream config;
std::string configstring;
};
extern INIParser* Parse;
INIClassTest.cpp
#include "INIClassTest.h"
#include <iostream>
INIParser* Parse = new INIParser();
INIParser::INIParser()
{
returntestvar = 0;
testvar = 18;
std::string configstring = ".//config.ini";
}
void INIParser::WriteINI()
{
config.open("config.ini", std::ios::app);
WritePrivateProfileString("Test", "Test1", CStringify(testvar), configstring.c_str());
}
void INIParser::ReadINI()
{
config.open("config.ini", std::ios::app);
returntestvar = GetPrivateProfileInt("Test", "Test1", 0, configstring.c_str());
}
The above code creates an .ini file, but it doesn't edit it or return anything.

Answer 1

You should NOT be using an fstream at all to create/open the INI file manually. WritePrivateProfileString() and GetPrivateProfileInt() handle that for you.
Also, if you read their documentation, you would see that you SHOULD NOT use a relative path for the INI file, or else the file will be relative to the Windows installation folder, not your app folder. So, you probably ARE reading/writing the INI file, just not where you are expecting from/to. If you want your INI file to be relative to your app's folder, you need to retrieve the path of your app's folder 1 and append the INI filename to it.
1: that is really not a good idea in general, though. Depending on where you install your app, the user might not have write access to that folder. You should instead use SHGetFolderPath() or SHGetKnownFolderPath() to get the user's local %AppData% folder, then create your own subfolder inside of it, and then create your INI file inside of that subfolder.
Try this instead:
#include <Windows.h>
#include <iostream>
#include <string>
#define CStringify(x) std::to_string(x).c_str()
std::string GetAppFolder();
std::string GetINIPath();
void WriteINI();
void ReadINI();
int testvar = 12;
int returntestvar = 0;
std::string configstring = GetINIPath();
int main()
{
WriteINI();
ReadINI();
std::cout << returntestvar << std::endl;
std::cin.get();
return 0;
}
std::string GetAppFolder()
{
char szFileName[MAX_PATH];
DWORD len = GetModuleFileName(NULL, szFileName, MAX_PATH);
std::string result(szFileName, len);
std::string::size_type pos = result.find_last_of("\\/");
result.resize(pos+1);
return result;
}
std::string GetINIPath()
{
return GetAppFolder() + "config.ini";
}
void WriteINI()
{
WritePrivateProfileString("Test", "Test1", CStringify(testvar), configstring.c_str());
}
void ReadINI()
{
returntestvar = GetPrivateProfileInt("Test", "Test1", 0, configstring.c_str());
}
The main reason your INIParser class fails is because your constructor is storing the INI file path in a local variable named configstring, instead of in the class's member also named configstring. Thus, the class member is blank when WriteINI() and ReadINI() are called.
Try this instead:
main.cpp
#include <iostream>
#include "INIClassTest.h"
int main()
{
Parse.WriteINI();
Parse.ReadINI();
std::cout << Parse.returntestvar << std::endl;
std::cin.get();
return 0;
}
INIClassTest.h
#pragma once
#include <string>
class INIParser
{
public:
INIParser();
void WriteINI();
void ReadINI();
int testvar;
int returntestvar;
std::string configstring;
};
extern INIParser Parse;
INIClassTest.cpp
#include <Windows.h>
#include "INIClassTest.h"
#include <string>
#define CStringify(x) std::to_string(x).c_str()
INIParser Parse;
static std::string GetAppFolder()
{
char szFileName[MAX_PATH];
DWORD len = GetModuleFileName(NULL, szFileName, MAX_PATH);
std::string result(szFileName, len);
std::string::size_type pos = result.find_last_of("\\/");
result.resize(pos+1);
return result;
}
static std::string GetINIPath()
{
return GetAppFolder() + "config.ini";
}
INIParser::INIParser()
{
returntestvar = 0;
testvar = 18;
configstring = GetINIPath();
}
void INIParser::WriteINI()
{
WritePrivateProfileString("Test", "Test1", CStringify(testvar), configstring.c_str());
}
void INIParser::ReadINI()
{
returntestvar = GetPrivateProfileInt("Test", "Test1", 0, configstring.c_str());
}