Save values to a config file

[J.Hilk]

@Sucharek

I actually have a ini file that I ship in one of my applications with the resource system. On startup I check, if my ini file exists in the relating appdata system.
If not I copy it from the resources.

This is made for Windows, but since its Qt, it should work just as well for Android.

Here are the bare bone functions:

//From to create class PreAppTasks:
void PreAppTasks::copyIniToDestDir()
{
    QFile *destFile = getDestIniFile();
    //QFile *orgFile  = getOrgIniFile();
    //in your case simply:
    QFile *orgFile = new File(":/config/config.ini");

    if(orgFile){
        if(destFile && destFile->exists()){
            //Both Files exists: implement your logic, for this case here
        } else {
            //DestFile does not exist (propably the first program execution) -> simply copy from install folder
            //But first, create the folder, if it does not exist
            QFileInfo info(destFile->fileName());
            info.setFile(info.absolutePath());
            if(!info.exists()){
                QDir d;
                d.mkpath(info.absoluteFilePath());
            }
            orgFile->copy(destFile->fileName());
        }
    }

    if(destFile){
        destFile->deleteLater();
        destFile = nullptr;
    }
    if(orgFile){
        orgFile->deleteLater();
        orgFile = nullptr;
    }
}


QFile *PreAppTasks::getDestIniFile()
{
//in your case:
    return new QFile(QStandardPaths::writableLocation(QStandardPaths::AppDataLocation) + QString("/config/config.ini"));
}

//In main.cpp (AFTER application instance creation!)
int main(int argc, char *argv[])
{
    QGuiApplication a(argc, argv);
    PreAppTasks::copyIniToDestDir();
....
    return a.exec();
}

[Sucharek]

@J-Hilk Thanks for the reply.
I'm not home right now, so I'll try it later.
Then I'll inform you if it works.

[Sucharek]

Hi, so I tried to add it to my code, but I don't know where.
Could you please tell me how to do it, or do I need to create a new C++ Class?

[SGaist]

@J-Hilk said in Save values to a config file:

//In main.cpp (AFTER application instance creation!)
int main(int argc, char *argv[])
{
QGuiApplication a(argc, argv);
PreAppTasks::copyIniToDestDir();
....
return a.exec();
}

[Sucharek]

@SGaist Yes, I've seen that, but I want to know where to put the code before.

//From to create class PreAppTasks:
void PreAppTasks::copyIniToDestDir()
{
    QFile *destFile = getDestIniFile();
    //QFile *orgFile  = getOrgIniFile();
    //in your case simply:
    QFile *orgFile = new File(":/config/config.ini");

    if(orgFile){
        if(destFile && destFile->exists()){
            //Both Files exists: implement your logic, for this case here
        } else {
            //DestFile does not exist (propably the first program execution) -> simply copy from install folder
            //But first, create the folder, if it does not exist
            QFileInfo info(destFile->fileName());
            info.setFile(info.absolutePath());
            if(!info.exists()){
                QDir d;
                d.mkpath(info.absoluteFilePath());
            }
            orgFile->copy(destFile->fileName());
        }
    }

    if(destFile){
        destFile->deleteLater();
        destFile = nullptr;
    }
    if(orgFile){
        orgFile->deleteLater();
        orgFile = nullptr;
    }
}


QFile *PreAppTasks::getDestIniFile()
{
//in your case:
    return new QFile(QStandardPaths::writableLocation(QStandardPaths::AppDataLocation) + QString("/config/config.ini"));
}

That code

[J.Hilk]

@Sucharek said in Save values to a config file:

Yes, I've seen that, but I want to know where to put the code before.

//From to create class PreAppTasks:

-> Functions/Code taken from a class that you yourself will have to create. In this case I originally named it PreAppTasks. That is why you will find the class Prefix PreAppTasks before the the function bodies. You can, but you don't have to use the same class name, that is up to your discretion.

...
Was a bit long for a comment so I shortened it.

[Sucharek]

@J-Hilk Ok, so I created a new class (PreAppTasks) and put in the code, but I have some errors:

out-of-line definition of 'copyIniToDestDir' does not match any declaration in 'PreAppTasks'
use of undeclared identifier 'getDestIniFile'
unknown type name 'File'
out-of-line definition of 'getDestIniFile' does not match any declaration in 'PreAppTasks'

my preapptasks.cpp

#include "preapptasks.h"
#include <QFile>
#include <QFileInfo>
#include <QDir>
#include <QStandardPaths>

PreAppTasks::PreAppTasks()
{

}

void PreAppTasks::copyIniToDestDir()
{
    QFile *destFile = getDestIniFile();
    //QFile *orgFile  = getOrgIniFile();
    //in your case simply:
    QFile *orgFile = new QFile(":/config/config.ini");

    if(orgFile){
        if(destFile && destFile->exists()){
            //Both Files exists: implement your logic, for this case here
        } else {
            //DestFile does not exist (propably the first program execution) -> simply copy from install folder
            //But first, create the folder, if it does not exist
            QFileInfo info(destFile->fileName());
            info.setFile(info.absolutePath());
            if(!info.exists()){
                QDir d;
                d.mkpath(info.absoluteFilePath());
            }
            orgFile->copy(destFile->fileName());
        }
    }

    if(destFile){
        destFile->deleteLater();
        destFile = nullptr;
    }
    if(orgFile){
        orgFile->deleteLater();
        orgFile = nullptr;
    }
}


QFile *PreAppTasks::getDestIniFile()
{
//in your case:
    return new QFile(QStandardPaths::writableLocation(QStandardPaths::AppDataLocation) + QString("/config/config.ini"));
}

[JonB]

@Sucharek said in Save values to a config file:

my preapptasks.cpp

So how does this compare to what is in your preapptasks.h?

[Sucharek]

@JonB Well, I didn't do anything with preapptasks.h.
What do I add in there?

[JonB]

@Sucharek
@J.Hilk gave you the definitions of a couple of methods of a PreAppTasks class. So in C++ you know you will need to provide the necessary class declaration in the .h file. Which I think from your error messages you have not done.

[Sucharek]

@JonB Ok, so I added
copyIniToDestDir();
getDestIniFile();
to the .h file, but I'm not sure what to declare there (err message: C++ requires a type specifier for all declarations).
I'm also having a problem with declaring the File variable.
On
QFile *orgFile = new File(":/config/config.ini");
when I try to declare it in the .h file (QFile File;), it doesn't fix the error message (unknown type name 'File').

[JonB]

@Sucharek
At this point you need to learn some basic C++ if you expect to code with Qt. You cannot do so without knowing the language,

[Sucharek]

Hi, so I've looked into it, and fixed almost all errors, except the "unknown type name 'File'".
I still can't figure out how to fix that one.

[J.Hilk]

@Sucharek thats actually a typo, and I now see, thats actually from my original code, I blame auto correction:

QFile *orgFile = new File(":/config/config.ini");
QFile *orgFile = new QFile(":/config/config.ini");

[Sucharek]

Hi, ok, when I get home, I'll try it.

[JonB]

@Sucharek
I don't know whether the other C++ experts would concur (comments always welcome!), but if you are intending to put

QFile *orgFile = new QFile(":/config/config.ini");

in the class member variables declaration in the .h file, I wouldn't. I would suggest such an initialisation (i.e. the new ... part) belongs better in the class constructor.

[Sucharek]

@JonB
As long as it works, I'm good with it.

I also find interesting that in this part of the code:

if(orgFile){
        if(destFile && destFile->exists()){
            qDebug() << "exists";
        } else {

If i change the resource prefix, or the config.ini name, it will STILL print "exists".
I also have another question. How do I write and read the file, now that the code probably works?

[artwaw]

@Sucharek https://doc.qt.io/qt-5/qfile.html is what you need.

Please learn at least the absolute basics of C++ (and Qt while we're at it - both are very well documented), if your intention is to make it work by using the code snippets provided by the others you'll get nowhere in the long run.

[Sucharek]

Hi, so I've looked into it and I can read from the file, but can't write.
I've tried multiple methods, but they don't seem to work.
my .cpp file:

#include "preapptasks.h"
QFile *orgFile;

PreAppTasks::PreAppTasks()
{

}

QFile *PreAppTasks::getDestIniFile()
{
//in your case:
    return new QFile(QStandardPaths::writableLocation(QStandardPaths::AppDataLocation) + QString("/config/config.ini"));
}

void PreAppTasks::copyIniToDestDir()
{
    orgFile = new QFile(":/config/config.ini");
    QTextStream in(orgFile);
    QFile *destFile = getDestIniFile();
    //QFile *orgFile  = getOrgIniFile();
    //in your case simply:

    if(orgFile){
        if(destFile && destFile->exists()){
                orgFile->open(QIODevice::ReadOnly | QIODevice::Text);
                qDebug() << orgFile->isOpen();
                QString line = in.readLine();
                qDebug() << line;
                orgFile->close();

                orgFile->open(stdin, QIODevice::ReadWrite | QIODevice::Text);
                qDebug() << orgFile->isOpen();
                orgFile->write("a");
                line = in.readLine();
                qDebug() << line;
                orgFile->close();
        } else {
            //DestFile does not exist (propably the first program execution) -> simply copy from install folder
            //But first, create the folder, if it does not exist
            QFileInfo info(destFile->fileName());
            info.setFile(info.absolutePath());
            if(!info.exists()){
                QDir d;
                d.mkpath(info.absoluteFilePath());
            }
            orgFile->copy(destFile->fileName());
        }
    }

    if(destFile){
        destFile->deleteLater();
        destFile = nullptr;
    }
    if(orgFile){
        orgFile->deleteLater();
        orgFile = nullptr;
    }
}

So, in
if(destFile && destFile->exists()){ ... }
I tried to read the contents of the file (currently 50), which worked, but writing doesn't.
EDIT: Also, when I try to read the line on ReadOnly mode, it works, but in ReadWrite mode, it doesn't even print anything.

P. S.: I'm sorry that you have to deal with me, but I just want to get this to work.

[J.Hilk]

@Sucharek said in Save values to a config file:

I'm sorry that you have to deal with me, but I just want to get this to work.

Don't worry, we all started somewhere sometime.

And I brought this path up, so I'll see it finished :P

Give me a some time, I'll make an working example