Sending QPixmap pointer via signal-slots, empty pixmap data - c++

Question

I have problem with sharing pointer to Pixmap via signal-slot mechanism.
Inside slot function I have correct QPixmap with fulled data.
In reciever I have unaccessible QPixmap with empty data.
Any ideas?
class A
{
public:
A:A():pixmap(0){};
void fillPixmap()
{
// correct Pixmap and data isn't null
}
public signals:
void sendQPixmapToB(QPixmap*);
private:
QPixmap *pixmap;
}
class B
{
public:
B:B(){};
public slots:
void recievePixmap(QPixmap* pixmap)
{
// here in debugger pixmap is unaccesible and data is 0
}
}
void onButtonClicked()
{
a.fillPixmap();
}
int main()
{
A a;
B b;
.....
connect(a, SIGNAL(sendQPixmapToB(QPixmap*)),b,SLOT(recievePixmap(QPixmap*)));
return 0;
}

Answer 1

I can not tell you what is wrong with your code because as you indicate you are showing a pseudo-code, so I will show you the correct way to do it.
#include <QGuiApplication>
#include <QPixmap>
#include <QTimer>
#include <QDebug>
class A: public QObject{
Q_OBJECT
public:
using QObject::QObject;
void sendPixmap(){
fillPixmap();
emit sendQPixmapToB(pixmap);
}
signals:
void sendQPixmapToB(const QPixmap & pixmap);
private:
void fillPixmap(){
pixmap = QPixmap(64, 64);
pixmap.fill(Qt::red);
}
QPixmap pixmap;
};
class B: public QObject{
Q_OBJECT
public:
using QObject::QObject;
public slots:
void recievePixmap(const QPixmap & pixmap){
qDebug()<<pixmap;
}
};
int main(int argc, char *argv[])
{
QGuiApplication a(argc, argv);
A obja;
B objb;
QObject::connect(&obja, &A::sendQPixmapToB, &objb, &B::recievePixmap);
QTimer::singleShot(1000, &obja, &A::sendPixmap);
return a.exec();
}
#include "main.moc"·