class derivated from QImage as parameter of signal

stephane78 0

Hi,
How to send an Image * (derivated from QImage) as parameter of a signal ?

I have put:

Q_DECLARE_METATYPE(Image)
Q_DECLARE_OPAQUE_POINTER(Image *)

stephane78 0

@mrjj ok my problem is solved I have replaced void mysignal(Image ,QString &) by void mysignal(Image,QString *) and now it works , thanks.

mrjj

Hi
Sending a pointer requires nothing extra as its a value and can be copied and queued by default.
So you can just do it.

signals:
    void mysignal(Image *);
public slots:
    void myslot(Image *);

    connect(this, &MainWindow::mysignal, this, &MainWindow::myslot );
    auto test = new Image;
    emit mysignal(test);

and it will work.

stephane78 0

@mrjj thank you but is it possible to send as parameter of a signal a QString & ?
because my signal is mysignal(Image*,QString &) and I don't receive the signal
it is emitted from the end of the function run from a class derivated from QThread to the mainwindow.

mrjj

@stephane78-0

Hi
QString already works in any combination so that should not be it.
mysignal(Image*,QString &) should also just work. ( slot has to match of cause )

So i think it something else :)

stephane78 0

@mrjj ok my problem is solved I have replaced void mysignal(Image ,QString &) by void mysignal(Image,QString *) and now it works , thanks.

SGaist

Hi,

Why are you sending a pointer to a QString ?

stephane78 0

@SGaist I send the pointer on the resulting image and the pointer on the filename of the original image because in my slot I compute the filename of the resulting image and I display this image.But with the pointer on QString as parameter in the signal it works

SGaist

Then you should rather use a const reference. But since you embed that file path in your class, why not use that ?