How do I create a simple Qt console application in 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

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 5

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...

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