Qt5 CMake QThread: the signal from abstract base class is not connected to the slot in another t-CodePudding

I implemented a hierarchy of classes to handle sensor interaction in a multithreaded QThread-based manner, as how it is recommended in Qt documentation. Here I have the header file types.h with the abstract base sensor reader class:

#include <QtCore>
class QAbstractSensorReader: public QObject
{   Q_OBJECT
protected slots:
    virtual void ReadData() = 0;
public slots:
    virtual void RunPoll() = 0;
signals:
    void acquired();
};

In the file serial.h implementing the actual sensor reader I have the following text:

#include "types.h"
class QBaseSerialSensorReader: public QAbstractSensorReader
{
    Q_OBJECT
private:
    /*===*/
protected:
    QTextStream ttyout;
    QTimer* poll_timer;
    virtual void ReadData();
public:
    QBaseSerialSensorReader(const QString device);
    virtual ~QBaseSerialSensorReader();
    virtual void RunPoll();
};

The signal acquired() is emitted in the ReadData() handler when the data packet is assembled completely during the sensor poll. The slot RunPoll() is used to initialize and start a timer. Then I implemented the controller class:

#include "serial.h"
class QSensor: public QObject
{
    Q_OBJECT
private:
    QThread reader_thread;
    QBaseSerialSensorReader* reader;

public:
    QSensor()
{
    reader = new QBaseSerialSensorReader();
    reader->moveToThread(&reader_thread);
    connect(&reader_thread, &QThread::finished, reader, &QObject::deleteLater);
    connect(this, &QSensor::RunReader, reader, &QAbstractSensorReader::RunPoll);
    connect(reader, &QBaseSerialSensorReader::acquired, this, &QSensor::Packet);
    reader_thread.start();
}

    void Start() {emit RunReader();}
    virtual ~QSensor();
public slots:
    void Packet(){ttyout << "ACQUIRED!";}
signals:
    void RunReader();
};

Then the application:

#include "controller.h"
int main(int argc, char** args)
{
    QCoreApplication app(argc, args);
    QSensor sensor();
    sensor.Start();
    sleep(10);
    return 0;
}

exploits the hierarchy.

The CMake file contains the following text:

find_package(Qt5 REQUIRED COMPONENTS Core SerialPort)
set(CMAKE_AUTOMOC ON)
qt5_wrap_cpp(MOC_SOURCES
    include/types.h
    include/serial.h
    include/contoller.h
    )
set(LIBRARY_SOURCES
    ${MOC_SOURCES}
    src/util.cpp
    src/serial.cpp
    src/controller.cpp
    )
add_library(sensor-serial SHARED ${LIBRARY_SOURCES})
target_link_libraries(sensor-serial Qt5::Core Qt5::SerialPort)
add_executable(library-init-test
    tests/library-init-test.cpp
    )
target_link_libraries(library-init-test
    Qt5::Core Qt5::SerialPort
    sensor-serial
    )

The problem is that the signal QSensor::RunReader is successfully connected to QAbstractSensorReader::RunPoll slot: the virtual function QBaseSerialSensorReader::RunPoll() is called. The timer is also started and the ReadData() function works emitting the acquired signal. But this signal then does not seem to be connected to the QSensor::Packet() slot neither from QAbstractSensorReader nor from QBaseSerialSensorReader namespace.

Could you please try to explain what wrong is happening with this code?

CodePudding user response：

You are not entering application event loop. Remove sleep from main function and call QCoreApplication::exec. I.e. replace these lines

sleep(10);
return 0;

with

return app.exec();