How do I create a simple Qt console application in C++? - c++

Question

I was trying to create a simple console application to try out Qt's XML parser. I started a project in VS2008 and got this template:
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
return a.exec();
}
Since I don't need event processing, I was wondering whether I may get into trouble if I neglect to create a QCoreApplication and running the event loop. The docs state that it's recommended in most cases.
For the sake of curiosity however, I am wondering how could I make some generic task execute on the event loop and then terminate the application. I was unable to google a relevant example.

Answer 1

Here is one simple way you could structure an application if you want an event loop running.
// main.cpp
#include <QtCore>
class Task : public QObject
{
Q_OBJECT
public:
Task(QObject *parent = 0) : QObject(parent) {}
public slots:
void run()
{
// Do processing here
emit finished();
}
signals:
void finished();
};
#include "main.moc"
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
// Task parented to the application so that it
// will be deleted by the application.
Task *task = new Task(&a);
// This will cause the application to exit when
// the task signals finished.
QObject::connect(task, SIGNAL(finished()), &a, SLOT(quit()));
// This will run the task from the application event loop.
QTimer::singleShot(0, task, SLOT(run()));
return a.exec();
}

Answer 2

Don't forget to add the
CONFIG += console
flag in the qmake .pro file.
For the rest is just using some of Qt classes.
One way I use it is to spawn processes cross-platform.

Answer 3

You don't need the QCoreApplication at all, just include your Qt objects as you would other objects, for example:
#include <QtCore>
int main()
{
QVector<int> a; // Qt object
for (int i=0; i<10; i++)
{
a.append(i);
}
/* manipulate a here */
return 0;
}

Answer 4

I managed to create a simple console "hello world" with QT Creator
used creator 2.4.1 and QT 4.8.0 on windows 7
two ways to do this
Plain C++
do the following
File- new file project
under projects select : other Project
select "Plain C++ Project"
enter project name
5.Targets select Desktop 'tick it'
project managment just click next
you can use c++ commands as normal c++
or
QT Console
File- new file project
under projects select : other Project
select QT Console Application
Targets select Desktop 'tick it'
project managment just click next
add the following lines (all the C++ includes you need)
add "#include 'iostream' "
add "using namespace std; "
after QCoreApplication a(int argc, cghar *argv[])
10 add variables, and your program code..
example: for QT console "hello world"
file - new file project 'project name '
other projects - QT Console Application
Targets select 'Desktop'
project management - next
code:
#include <QtCore/QCoreApplication>
#include <iostream>
using namespace std;
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
cout<<" hello world";
return a.exec();
}
ctrl -R to run
compilers used for above MSVC 2010 (QT SDK) , and minGW(QT SDK)
hope this helps someone
As I have just started to use QT recently and also searched the Www for info and examples to get started with simple examples still searching...

Answer 5

You could fire an event into the quit() slot of your application even without connect().
This way, the event-loop does at least one turn and should process the events within your main()-logic:
#include <QCoreApplication>
#include <QTimer>
int main(int argc, char *argv[])
{
QCoreApplication app( argc, argv );
// do your thing, once
QTimer::singleShot( 0, &app, &QCoreApplication::quit );
return app.exec();
}
Don't forget to place CONFIG += console in your .pro-file, or set consoleApplication: true in your .qbs Project.CppApplication.

Answer 6

You can call QCoreApplication::exit(0) to exit with code 0

Answer 7

Had the same problem. found some videos on Youtube.
So here is an even simpler suggestion. This is all the code you need:
#include <QDebug>
int main(int argc, char *argv[])
{
qDebug() <<"Hello World"<< endl;
return 0;
}
The above code comes from
Qt5 Tutorial: Building a simple Console application by
Dominique Thiebaut
http://www.youtube.com/watch?v=1_aF6o6t-J4