error When use moveToThread

[hikaris]

Hi, rencently I'm coding on a video processing program, and trying to move the time cost processing in to another thread, by subclassing QObject and move it to another thread by moveToThread.

class VideoEncoder : public QObject
{
    VideoEncoder();
}

Here's an another class called VideoController, which manages VideoEncoder:

#include <QThread>
#include "VideoEncoder.h"
class VideoController : public QWidger
{
    ....
public:
    void init();
private:
    QThread *encoderThread_;
    VideoEncoder *videoEncoder_;

here's my moveToThread code.

void VideoController::init()
{
    videoEncoder_ = new VideoEncoder;
    encoderThread_ = new QThread;
    videoEncoder_->moveToThread(encoderThread_);  // Get Errors!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
    // cannot initialize object parameter of type 'QObject' with an expression of type 'VideoEncoder'
}

If I move the line of

#include "VideoEncoder.h"

from header file to cpp file,
and add a forward declaration

class VideoEncoder

in header file
The error disappears.

Could someone help me through it. It really confuses me.

[JohanSolo]

Not directly related to your question, but your VideoEncoder is a QWidget, and therefore must lie in the main thread. GUI objects must live in the main thread.

[Christian Ehrlicher]

@hikaris said in error When use moveToThread:

The error disappears.

Please show the full code. I would guess you create a circular include.

[hikaris]

@JohanSolo nope, VideoEncoder is a QObject. VideoController is a QWidget, and it lives in main thread.

[kshegunov]

Did you forget to add Q_OBJECT for VideoEncoder?

[hikaris]

@kshegunov no, I did add Q_OBJECT for VideoEncoder, and also VideoController

[mranger90]

@hikaris After adding Q_OBJECT did you do a clean/run qmake/rebuild ?:

[Christian Ehrlicher]

Again: please ost your both headers. I'm pretty sure there is a circular include which prevents the compiler from knowing that your class derives from QObject - that's exactly what the error message tells you, nothing else.

[hikaris]

@Christian-Ehrlicher you are right, thank you.