Cfrgtkky

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.

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();

}

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.

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;

}

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

1. File- new file project


2. under projects select : other Project


3. select "Plain C++ Project"


4. enter project name
   5.Targets select Desktop 'tick it'


5. project managment just click next


6. you can use c++ commands as normal c++

or

QT Console

1. File- new file project


2. under projects select : other Project


3. select QT Console Application


4. Targets select Desktop 'tick it'


5. project managment just click next


6. add the following lines (all the C++ includes you need)


7. add "#include 'iostream' "


8. add "using namespace std; "


9. 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...

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

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 processes 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.