I have text files in my resource file and I'd like to be able to provide a path for this file to std::ifstream. Neither :\file_name.txt nor ..\file_name.txt works.
Does anyone know how to fix it?
Qt resource files are not filesystem files. Those files are loaded in memory as static char arrays. You can see for yourself looking in your build directory for qrc_*.cpp files. You can get data from there if you want, or you might want to use QTextStream for reading those, using the QIODevice constructor with a QFile.
You don't specify what you want to do exactly, but this is a sample that reads what is inside the file:
#include <QtCore/QCoreApplication>
#include <QTextStream>
#include <QFile>
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QFile file(":/test.txt");
QTextStream stream(&file);
if (!file.open(QIODevice::ReadOnly)) {
qFatal("Failed to open file.");
return -1;
}
QString text = stream.readAll();
if (text.isNull()) {
qDebug("Failed to read file.");
return -1;
}
qDebug("File content is: %s. Bye bye.", qPrintable(text));
return 0;
}
Related
It's strange, I add desired file into the resources via Add Existing Files..., the file is there. I run qmake ("Build->Run qmake") to make the file available.
The first issue: I can't write anything into the file from output terminal! But when I manually write into the file, the output terminal shows the change every time I run it. Second issue: it still says QIODevice::read: device not open !
Here's my code:
#include <QCoreApplication>
#include <QDebug>
#include <QFile>
#include <QString>
#include <QTextStream>
#include <iostream>
void wFile(QString Filename)
{
QFile nFile(Filename);
QTextStream str(&nFile);
qDebug() << "what do you want to write in the desired file: ";
str.readLine();
if (!nFile.open(QFile::WriteOnly | QFile::Text))
{
qDebug() << "could not open the file";
return;
}
nFile.flush();
nFile.close();
}
void read (QString Filename){
QFile nFile(Filename);
if(!nFile.open(QFile::ReadOnly | QFile::Text))
{
qDebug() << "could not open file for reading";
return;
}
QTextStream in(&nFile);
QString nText = in.readAll();
qDebug() << nText;
nFile.close();
}
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QString nFilename =":/MyFiles/DocumentArminV.txt";
wFile(nFilename);
read(nFilename);
return a.exec();
}
And here's output terminal of the code:
The files saved in a qresource are read-only since they are part of the executable so you can not write or modify them.
docs:
Currently, Qt always stores the data directly in the executable, even on Windows, macOS, and iOS, where the operating system provides native support for resources. ...
It's strange, I add desired file into the resources via Add Existing Files..., the file is there. I run qmake ("Build->Run qmake") to make the file available.
The first issue: I can't write anything into the file from output terminal! But when I manually write into the file, the output terminal shows the change every time I run it. Second issue: it still says QIODevice::read: device not open !
Here's my code:
#include <QCoreApplication>
#include <QDebug>
#include <QFile>
#include <QString>
#include <QTextStream>
#include <iostream>
void wFile(QString Filename)
{
QFile nFile(Filename);
QTextStream str(&nFile);
qDebug() << "what do you want to write in the desired file: ";
str.readLine();
if (!nFile.open(QFile::WriteOnly | QFile::Text))
{
qDebug() << "could not open the file";
return;
}
nFile.flush();
nFile.close();
}
void read (QString Filename){
QFile nFile(Filename);
if(!nFile.open(QFile::ReadOnly | QFile::Text))
{
qDebug() << "could not open file for reading";
return;
}
QTextStream in(&nFile);
QString nText = in.readAll();
qDebug() << nText;
nFile.close();
}
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QString nFilename =":/MyFiles/DocumentArminV.txt";
wFile(nFilename);
read(nFilename);
return a.exec();
}
And here's output terminal of the code:
The files saved in a qresource are read-only since they are part of the executable so you can not write or modify them.
docs:
Currently, Qt always stores the data directly in the executable, even on Windows, macOS, and iOS, where the operating system provides native support for resources. ...
It's strange, I add desired file into the resources via Add Existing Files..., the file is there. I run qmake ("Build->Run qmake") to make the file available.
The first issue: I can't write anything into the file from output terminal! But when I manually write into the file, the output terminal shows the change every time I run it. Second issue: it still says QIODevice::read: device not open !
Here's my code:
#include <QCoreApplication>
#include <QDebug>
#include <QFile>
#include <QString>
#include <QTextStream>
#include <iostream>
void wFile(QString Filename)
{
QFile nFile(Filename);
QTextStream str(&nFile);
qDebug() << "what do you want to write in the desired file: ";
str.readLine();
if (!nFile.open(QFile::WriteOnly | QFile::Text))
{
qDebug() << "could not open the file";
return;
}
nFile.flush();
nFile.close();
}
void read (QString Filename){
QFile nFile(Filename);
if(!nFile.open(QFile::ReadOnly | QFile::Text))
{
qDebug() << "could not open file for reading";
return;
}
QTextStream in(&nFile);
QString nText = in.readAll();
qDebug() << nText;
nFile.close();
}
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QString nFilename =":/MyFiles/DocumentArminV.txt";
wFile(nFilename);
read(nFilename);
return a.exec();
}
And here's output terminal of the code:
The files saved in a qresource are read-only since they are part of the executable so you can not write or modify them.
docs:
Currently, Qt always stores the data directly in the executable, even on Windows, macOS, and iOS, where the operating system provides native support for resources. ...
I saved the QString in the file like this:
QString str="blabla";
QByteArray _forWrite=QByteArray::fromHex(str.toLatin1());
f.write(_forWrite); // f is the file that is opened for writing.
Then when I read the file I use QFile::readAll() to take the QByteArray but I don't know how to convert it to QString.
I tried to use the constructor that uses QByteArray but It didn't work out. I tried also with QByteArray::data() but same result. What I do wrong ?
It's not clear why you are calling QByteArray::fromHex at all. toLatin1() already return you QByteArray where each symbol encoded with one byte.
[UPDATE]
You should NOT call QByteArray::fromHex at all, because:
invalid characters in the input are skipped
And invalid characters are characters that are not the numbers 0-9 and the letters a-f
You can use QDataStream
#include <QApplication>
#include <QDataStream>
#include <QByteArray>
#include <QFile>
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QString strToWrite = "blabla";
QFile fileToWrite("file.bin");
QDataStream dataStreamWriter(&fileToWrite);
fileToWrite.open(QIODevice::WriteOnly);
dataStreamWriter << strToWrite;
fileToWrite.close();
QString strToRead = "";
QFile fileToRead("file.bin");
QDataStream dataStreamReader(&fileToRead);
fileToRead.open(QIODevice::ReadOnly);
dataStreamReader >> strToRead;
fileToRead.close();
qDebug() << strToRead;
return app.exec();
}
Output : "blabla"
I wrote a simple code to open plain text file with Qt 5's QFile as seen below;
// main.cpp
#include <iostream>
using std::endl;
using std::cout;
#include <QCoreApplication>
#include <QFile>
#include <QIODevice>
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QFile plainFile("plain.txt");
if(plainFile.open(QIODevice::ReadOnly | QIODevice::Text))
{
cout << "File opened successfull" << endl;
plainFile.close();
}
else{
cout << "could not open file." << endl;
}
return a.exec();
}
The output when compiled and run is "could not open file".
What am I do wrong?
Probably because plain.txt does not exist in the current working directory or in the PATH. Make sure the file is in the working directory or pass the absolute path to QFile.
Also see what QFile::exists returns.
Wouter Huysentruit is right.
Remember, that, by default, when you running application from QtCreator working directory is, for example, C:\Projects\build-Test-Desktop_Qt_5_1_0_MinGW_32bit-Debug. But your .exe file lay in C:\Projects\build-Test-Desktop_Qt_5_1_0_MinGW_32bit-Debug\Debug.
When you run your .exe directly, then working directory will be that folder, where this file is layed now.
So, you can:
1.Pass absolute path.
2.Put file in current working directory (I suppose that it is best solution).
3.Just change relative path: QFile plainFile("debug/plain.txt");