Aloha,
Im developing a small "ServerManager" for myself using QT (C++).
Anything worked till this point:
I use QSettings to store all relevant Settings (like Server, installed Plugins and so on).
As I didn't want to instanciate the QSettings class everywhere I have to use it, i thought i could try to instanciate it one time in the main.cpp and make it available using the qApp->setProperty() method.
How i setup the QSettings class:
QSettings* Settings = new QSettings(".\\Settings.ini", QSettings::IniFormat);
How i "publish" it:
qApp->setProperty("Settings", QVariant::fromValue<QSettings*>(Settings));
And finally. If i use it like this:
QSettings* Settings = qApp->property("Settings").value<QSettings*>();
Settings->beginGroup("Servers");
The whole application crashed with an SIGSEGV signal (Segmentation fault).
Stacktrace: Stacktrace http://host-it.tk/Upload/53ab11da0d706/37.PNG
I really got no clue why this happens.
Maybe the solution is obvious, but this is my "first real" Application.
It seems like I got the well known "tunnel view".
Thanks for your time!
Relevant code parts: http://pastebin.com/VzZ9uuJi
QT-Version: 5.2.1
Since a QSettings* is not a usual QVariant type, you would have to declare it.
Q_DECLARE_METATYPE(QSettings*);
This is not the usual way to share QSettings, though. Since it is in INI format, consider just passing the location to the INI file with absolute paths instead:
QFileInfo path(".\\Settings.ini");
qApp->setProperty("SettingsLocation", path.absoluteFilePath());
Then later:
QSettings Settings(qApp->property("SettingsLocation").toString(), QSettings::IniFormat);
Settings.beginGroup("Servers");
Related
I am trying to securely clear out a directory using SDelete. I know that this is used from the Command line, but how I would I go about automatically clearing the directory from my C++ code, also using Qt if this has a built any built in functions. I could not find anything with searching and this is my first time doing something like this. Any help would be greatly appreciated, thanks.
It is good that you're not trying to re-create the functionality of SDelete. It would be a LOT of work to do as good as a job as what SDelete does. Invoking the existing application is a wise choice.
Now, on to your question... If you want to use QT, then what you need is something like this:
QString path = QString("sdelete", QStringList() << "Bogus.txt");
QProcess sdelete;
sdelete.start( path );
sdelete.waitForFinished();
That will start the process sdelete with the parameter Bogus.txt and then wait until the application is finished.
More Info: https://doc.qt.io/archives/qt-4.8/qprocess.html#start
Edit from OP : I found that using the following worked for me with the argument being passed in being a QString.
QProcess::execute("sdelete -s path");
I'm an unfortunate beginner at C++ and using the Qt GUI designer program seemed perfect for my needs, except I'm having problems trying to write out the code necessary for this. I could use the QSettings string to store local settings on the hard drive, but I personally hate it when programs do the %HOME_LOCAL%\APPS_SETTINGS bull that some do. I need to save a text file for both settings and a local\host database, within the program directory, to remember strings to read from later.
What is the line of code I need to make use of a local host text database or is there a better option? And how can I store that with the local program inside its directory?
You can use QSettings with any file, with constructor QSettings::QSettings ( const QString & fileName, Format format, QObject * parent = 0 ).
To get the program directory, you can use QCoreApplication::applicationDirPath().
So, answer to your question, statement to put after creation of QApplication instance:
QSettings *settings = new QSettings(
QCoreApplication::applicationDirPath() + "/settings.ini",
QSettings::IniFormat,
qApp);
But, as noted in the comments under question, if you're making your program for general distribution, you should use the OS default. Examine all the constructors of QSettings to see what it can do. User does not often have write permission in the application directory. Note that you can also store settings to Windows registry with QSettings::NativeFormat.
Im trying to create ini file that will hold me the configuration data, I have singletone class
that setting the QSettings object like this :
... #DEFINE CONFIG_FILE_NAME "myconfig.ini"
m_pSettings = new QSettings(QDir::currentPath()+"/"+CONFIG_FILE_NAME,QSettings::IniFormat);
this is accourding the document, but when i look in my application dir, there is none myconfig.ini file created, what im doing wrong ?
I believe in order to force QSettings file to appear you would need to set at least one value in it and then call sync() method. See if an example below would work for you:
QSettings* settings = new QSettings(QDir::currentPath() + "/my_config_file.ini", QSettings::IniFormat);
settings->setValue("test", "value");
settings->sync();
hope this helps, regards
I dont think that "/"+CONFIG_FILE_NAME return the expected result. May be the cause of your problem..
Anyway operator +() is present in QString class so QDir::currentPath() + "/my_config_file.ini" must work fine.
I'm trying to use QHttp for an update app. But there is a problem for me which I can't solve.
I try to download a file (works perfectly) but if there is no connection to the internet, the file is created but has 0 bytes. My old file is then overwritten with the empty file, which is not so good for the application trying to use the file. What I need is to check if the computer is connected to the internet.
Note: proxy may set. I used this example from Qt's homepage.
You should switch to the QNetworkAccessManager as Mike Suggested, here is an example of a slot on the finished() signal:
void ApplicationUpdate::replyFinishedhttpGetChangeLog(QNetworkReply* myReply) {
if (myReply->error() != QNetworkReply::NoError)
{
QByteArray returnedData = myReply->readAll();
if (returnedData.size() > 0) {
if( m_fileChangeLog->exists() )
{
m_fileChangeLog->close();
m_fileChangeLog->remove();
}
m_fileChangeLog->open(QIODevice::ReadWrite);
QDataStream out( m_fileChangeLog );
out.writeRawData(returnedData.data(), returnedData.size());
m_fileChangeLog->flush();
m_fileChangeLog->close();
}
}
}
Firstly, you should probably now be using QNetworkAccessManager rather than QHttp.
Using either of them, you should do a dummy query to a site you pretty much always know will be up (e.g. http://www.google.com/) and use that as a test to see if you have an internet connection.
A better way of doing this would be instead to use QNetworkAccessManager to read into a QByteArray and then check it isn't empty before writing to your file.
Whenever you write a file that might already exist, you should create a QTemporaryFile first, then, after successful download, rename it to the final name.
i ran into the same problem, after a bit of poking around, I've isolated the problem down to the project configuration file (.pro), in the broken configuration I was linking the networking library explicitly with the statement : "LIBS += -lQtNetwork". In the working configuration, I used the more formal (and qt compilant) approach of delcaring what Qt components are included in the project, like so: "QT = core gui network xml", adjust accordingly for your sitiation, the netowkring slots did not work on windows when explicitly linked but did work on linux. Using the qt compilant approach works on both platforms.
linux: $HOME/.config
windows: %APPDATA%
mac os: $HOME/.config
It can be set using http://qt-project.org/doc/qt-4.8/qsettings.html#setPath, but it seems as I am not able to retrieve it.
http://qt-project.org/doc/qt-4.8/qlibraryinfo.html#location QLibraryInfo::LibrariesPath returns the system wide settings dir, which is not what I want.
Any ideas, or do I have to code it separately for each platform?
€: I want to create a sub directory, and store files into it. (You may punish me if this is a bad idea)
This might not answer your question directly: if you want to store per-user persistent data, shouldn't you use QDesktopServices::storageLocation(QDesktopServices::DataLocation) instead?
This is a nasty workaround. First you create QSettings, then get its location.
QSettings cfg(QSettings::IniFormat, QSettings::UserScope,
"organization", "application");
QString config_dir = QFileInfo(cfg.fileName()).absolutePath() + "/";
Credits go to the Qt Centre forum.
QSettings stores the default config in the user AppData directory. See documentation for QSettings. Also this code instructs to store the config in the Ini file format.
this works on both qt 4 and qt 5
QApplication::setApplicationName("MyApp");
QApplication::setOrganizationName("Me");
QString homePath;
#if QT_VERSION >= 0x050000
homePath = QStandardPaths::writableLocation(QStandardPaths::DataLocation);
#else
homePath = QDesktopServices::storageLocation(QDesktopServices::DataLocation);
#endif
Why do you need to know the settings path? If you are going to put settings in it, you could use QSettings. I could see making a subdirectory to hold various settings, but it seems like the easiest way would be to use QSettings directly.
As far as I can tell, you can't retrieve the path. In the Qt source, src/corelib/io/qsettings.cpp, there is a function to get the path:
static QString getPath(QSettings::Format format, QSettings::Scope scope)
{
...
but it's not accessible from code using Qt. You can't copy it and use it either, because it uses internal Qt globals to store the path...
EDIT: A solution was posted, using QDesktopServices.storageLocation(QDesktopServices.DataLocation) but it doesn't do exactly what the question was asking for, i.e. if I set a custom path using QSettings.setPath() it doesn't reflect the change.
What platform are you at?
Might be related or not but in windows, the default is to write QSettings to the registry.
I read more into the question than there was as it was originally posted. It is clearer after the edits. Ok, so can't you use..
QString QSettings::fileName () const
Returns the path where settings are written to using this QSettings object are stored.
On Windows, if the format is QSettings::NativeFormat, the return value is a system registry path, not a file path.