Qthread and workers classes arguments

dedetuga

hi, I'm having some bad time trying understand how to use qthreads,
I have some code to be runned in a parallel thread, for that I used Qthread with classes, for that I used this page as sample QThreads general usage .
I took a wile to understand how implement this code is my first time implementing threads in codding.
I'm managed to put the code running in the thread and worker but I need to pass some data from variables to the worker. I can't find any complete sample of "how to do it" I only find some brief explanations with code fragments and I'm not able to understand.

how can I do that?

Thanks

dedetuga

Solved!!!!!!!!!!!!!!!!!!!!!

I miss a default value...I replace:

explicit Worker(QObject *parent = nullptr, int variable);

by:

 explicit Worker(QObject *parent = nullptr, int variable = 0);

And everything start working, there is my sample code for future references to noobs like me.

mainwindow.cpp

        QThread* threadtest = new QThread;
        Worker* worker = new Worker(nullptr, 100);

        worker->moveToThread(threadtest);
        connect(worker, SIGNAL (finished()), threadtest, SLOT (quit()));
        connect(worker, SIGNAL (finished()), worker, SLOT (deleteLater()));
        connect(threadtest, SIGNAL (finished()), threadtest, SLOT (deleteLater()));

        threadtest->start();

worker.cpp

Worker::Worker(QObject *parent, int variable) : QObject(parent)
{
    int intvar = variable;
}

worker.h

class Worker : public QObject
{
    Q_OBJECT
public:
    explicit Worker(QObject *parent = nullptr, int variable = 0);
...
...
...

jsulm

@dedetuga When exactly do you need to pass parameters?
You can simply pass the parameters when you create your worker:

MyWorker *worker = new MyWorker(param1, param2, ...);

Or you can pass them later using signals/slots.

dedetuga

Hi @jsulm, thanks for reply!
I can pass the parameters any time, but may for now its better pass it at the start, following your sample...if i pass the parameter when creating my worker how do i receive them?

in mainwindow.cpp

...
QThread* threadtest = new QThread;
MyWorker *worker = new MyWorker(param1, param2, ...);
...

in worker.cpp

...
Worker::Worker(QObject *parent) : QObject(parent)
{ 
   
}
...

in worker.h

...
public:
    explicit Worker(QObject *parent = nullptr);
...

I Have no idea how to handle the parameters in worker.cpp and worker.h files to be able to receive them.
How can I do it?

SGaist

Hi,

You have to declare a constructor that takes these parameters and not only the "QObject *parent".

dedetuga

hi, @SGaist, thanks for reply!

Can you please sample some code? I already try but I don't know how to do it and i end every time with errors.

thanks

SGaist

What did you try ?

dedetuga

main:

Worker* worker = new Worker(nullptr, 10);

w.cpp

Worker::Worker(QObject *parent, int variable) : QObject(parent)

w.h

    explicit Worker(QObject *parent = nullptr, int variable);

SGaist

You should put the parent parameter as last with the usual default value.

Otherwise, that's correct.

What error do you get ?

dedetuga