CODEWITHSUNDEEP
qtresourcesexitquit
daisy
daisy

Reputation: 23489

Correct way to quit a Qt program?

How should I quit a Qt Program, e.g when loading a data file, and discovered file corruption, and user need to quit this app or re-initiate data file?

Should I:

  1. call exit(EXIT_FAILURE)
  2. call QApplication::quit()
  3. call QCoreApplication::quit()

And difference between (2) and (3)?

Upvotes: 156

Views: 203570

Answers (6)

laurent
laurent

Reputation: 90736

You can call qApp->exit();. I always use that and never had a problem with it.

If you application is a command line application, you might indeed want to return an exit code. It's completely up to you what the code is.

Upvotes: 33

Jellybaby
Jellybaby

Reputation: 986

While searching this very question I discovered this example in the documentation.

QPushButton *quitButton = new QPushButton("Quit");
connect(quitButton, &QPushButton::clicked, &app, &QCoreApplication::quit, Qt::QueuedConnection);

Mutatis mutandis for your particular action of course.

Along with this note.

It's good practice to always connect signals to this slot using a QueuedConnection. If a signal connected (non-queued) to this slot is emitted before control enters the main event loop (such as before "int main" calls exec()), the slot has no effect and the application never exits. Using a queued connection ensures that the slot will not be invoked until after control enters the main event loop.

It's common to connect the QGuiApplication::lastWindowClosed() signal to quit()

Upvotes: 2

Bill
Bill

Reputation: 11822

QApplication is derived from QCoreApplication and thereby inherits quit() which is a public slot of QCoreApplication, so there is no difference between QApplication::quit() and QCoreApplication::quit().

As we can read in the documentation of QCoreApplication::quit() it "tells the application to exit with return code 0 (success).". If you want to exit because you discovered file corruption then you may not want to exit with return code zero which means success, so you should call QCoreApplication::exit() because you can provide a non-zero returnCode which, by convention, indicates an error.

It is important to note that "if the event loop is not running, this function (QCoreApplication::exit()) does nothing", so in that case you should call exit(EXIT_FAILURE).

Upvotes: 176

user3777664
user3777664

Reputation: 7

//How to Run App

bool ok = QProcess::startDetached("C:\\TTEC\\CozxyLogger\\CozxyLogger.exe");
qDebug() <<  "Run = " << ok;


//How to Kill App

system("taskkill /im CozxyLogger.exe /f");
qDebug() << "Close";

example

Upvotes: -12

Durgarao Maruboina
Durgarao Maruboina

Reputation: 49

If you're using Qt Jambi, this should work:

QApplication.closeAllWindows();

Upvotes: 0

Petr Tripolsky
Petr Tripolsky

Reputation: 1613

if you need to close your application from main() you can use this code

int main(int argc, char *argv[]){
QApplication app(argc, argv);
...
if(!QSslSocket::supportsSsl()) return app.exit(0);
...
return app.exec();
}

The program will terminated if OpenSSL is not installed

Upvotes: -1

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