A while(1) C function to run in Qt

[wysota]

C++ compilers don't care if you call "C" or "C++" functions in your programs.

[020394]

C++ compilers don't care if you call "C" or "C++" functions in your programs.

Oh wait, My "C" functions are in a .C file . So i am unable to do Worker *worker=new Worker at all .

[ChrisW67]

Wrap your plain functions in a class and the problem is solved. It really is not complicated. Here is a complete, threaded program that prints powers of two:

#include <QCoreApplication>
#include <QObject>
#include <QThread>
#include <QDebug>
 
// Plain function with C linkage declaration 
extern "C" {
    int multiplyByTwo(int i);
}
 
// Plain function impl
int multiplyByTwo(int i) { 
    return i * 2; 
}
 
 
 
class Worker : public QObject {
    Q_OBJECT
 
public:
    Worker();
    ~Worker();
public slots:
    void process();
signals:
    void finished();
private:
    // add your variables here
};
 
Worker::Worker() { } 
Worker::~Worker() { }
 
// Start processing data.
void Worker::process() {
    int value = 1;
    while (value < 1000000000) {
        qDebug() << value;
        value = multiplyByTwo(value);
    }
    emit finished();
}
 
 
int main(int argc, char **argv) {
    QCoreApplication app(argc, argv);
 
    QThread* thread = new QThread;
    Worker* worker = new Worker;
    worker->moveToThread(thread);
    QObject::connect(thread, SIGNAL(started()), worker, SLOT(process()));
    QObject::connect(worker, SIGNAL(finished()), thread, SLOT(quit()));
    QObject::connect(worker, SIGNAL(finished()), worker, SLOT(deleteLater()));
    QObject::connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));
    thread->start();
 
    QObject::connect(thread, SIGNAL(destroyed()), qApp, SLOT(quit()));
    return app.exec();
}
#include "main.moc"

#include <QCoreApplication>
#include <QObject>
#include <QThread>
#include <QDebug>

// Plain function with C linkage declaration 
extern "C" {
    int multiplyByTwo(int i);
}

// Plain function impl
int multiplyByTwo(int i) { 
    return i * 2; 
}



class Worker : public QObject {
    Q_OBJECT

public:
    Worker();
    ~Worker();
public slots:
    void process();
signals:
    void finished();
private:
    // add your variables here
};

Worker::Worker() { } 
Worker::~Worker() { }

// Start processing data.
void Worker::process() {
    int value = 1;
    while (value < 1000000000) {
        qDebug() << value;
        value = multiplyByTwo(value);
    }
    emit finished();
}


int main(int argc, char **argv) {
    QCoreApplication app(argc, argv);

    QThread* thread = new QThread;
    Worker* worker = new Worker;
    worker->moveToThread(thread);
    QObject::connect(thread, SIGNAL(started()), worker, SLOT(process()));
    QObject::connect(worker, SIGNAL(finished()), thread, SLOT(quit()));
    QObject::connect(worker, SIGNAL(finished()), worker, SLOT(deleteLater()));
    QObject::connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));
    thread->start();

    QObject::connect(thread, SIGNAL(destroyed()), qApp, SLOT(quit()));
    return app.exec();
}
#include "main.moc"

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[020394]

Thanks guys i have found another way to "Threading ", maybe wrongly executed .
I did it by declaring the "C" function into a function in the cpp file .
Then i used a Qtimer to connect the timer to the function and start it.

[wysota]

Thanks guys i have found another way to "Threading ", maybe wrongly executed .
I did it by declaring the "C" function into a function in the cpp file .
Then i used a Qtimer to connect the timer to the function and start it.

There is no threading here, timers do not spawn new threads.

[wiz29]

Try to use the QtConcurrent::run or the QtConcurrent::map instead the QThread.

[020394]

So when can I use the QTimer ? I am trying to use the QTimer to run a function along with the Gui. Is it the right way to ?

[wysota]

A timer is for running some code in a specific moment in time. It is handled by an event like (almost) everything else in Qt.

[020394]

A timer is for running some code in a specific moment in time. It is handled by an event like (almost) everything else in Qt.

Isnt It the same as running threads ? For now i am doing a school project with different groups all doing different part . for me i am doing the Gui. I need to integrate the rest of the codes my friends do . EG (Algorithm , Checking of a keypad. etc). Am i able to use QTimer for them since i want them to run at a specific moment of time when i am at the Gui page

[wysota]

Isnt It the same as running threads ?

No. If you are to eat lunch at 12 o'clock, it doesn't mean at 12 some other instance of yourself is spawned and eats a sandwich but rather you have to stop what you had been doing, take out a sandwich, unwrap it, eat it and then attend your other tasks.

[020394]

I see so threading is always running in the background . But i been using timer to check the current time(Updatiing the time on the Label) , Isnt that considered as threadings?

[wysota]

I see so threading is always running in the background . But i been using timer to check the current time(Updatiing the time on the Label) , Isnt that considered as threadings?

No. Timers have nothing to do with threading.