Qt emit signal and continue execution - qt

Question

I have something like that:
Prueba.h
#include <QObject>
class Prueba:public QObject
{
Q_OBJECT
private:
bool waiting;
public:
Prueba();
void test();
void fin();
signals:
void comenzo();
};
Prueba.cpp
#include "prueba.h"
#include <QDebug>
Prueba::Prueba()
{
waiting=true;
}
void Prueba::test()
{
qDebug()<<"Comenzando";
emit(comenzo());
while(waiting) {
qDebug()<<"Esperando";
}
qDebug()<<"Termino";
}
void Prueba::fin()
{
waiting=false;
}
Principal.h
#include <QObject>
#include "prueba.h"
class Principal:public QObject
{
Q_OBJECT
private:
Prueba * prueba;
public:
Principal();
private slots:
void processSignal();
};
Principal.cpp
#include <QDebug>
Principal::Principal()
{
prueba=new Prueba();
connect(prueba,SIGNAL(comenzo()),SLOT(processSignal()));
prueba->test();
}
void Principal::processSignal()
{
for(int i=0;i<1000;i++) {
qDebug()<<"Algo";
}
prueba->fin();
}
When I call prueba->test(), and it emit the signal "comenzo", Principal::proccessSignal is completely executed, and never enters to the cycle "while(waiting)". What I need to do for that the code inside the loop is executed?

Answer 1

My guess is your signal connection. By default Qt will execute your signal as a direct call to the slot the objects are in the same thread as you can see here:
QMetaObject::Connection QObject::connect(
const QObject * sender, const char * signal,
const char * method, Qt::ConnectionType type = Qt::AutoConnection) const
See Qt::ConnectionType here http://qt-project.org/doc/qt-5.0/qtcore/qt.html#ConnectionType-enum
So if you use
Qt::QueuedConnection
in your signal connection
connect(prueba,SIGNAL(comenzo()),SLOT(processSignal()), Qt::QueuedConnection);
It should work as expected. See
The slot is invoked when control returns to the event loop of the receiver's thread. The slot is executed in the receiver's thread.