How can i correctly make the definition of class in cpp

[dzeko1236]

Hello ,
I am really new in c++ development .

I created a class Backend .

In Backend.h I defined a constructor .
So I would like t redefine correctly my class In Backend.cpp

thank you

[dzeko1236]

this is the def in Backend.h

public:
    Backend(QObject *parent = nullptr): QObject(parent), m_fetchFrameTimer(this){
        connect(&m_fetchFrameTimer, & QTimer::timeout, this, &Backend::fetchNextDataFrame);
        m_fetchFrameTimer.setSingleShot(true);

        m_canDevice = QCanBus::instance()->createDevice(QStringLiteral("socketcan"), QStringLiteral("can0"));
        connect(m_canDevice, &QCanBusDevice::framesReceived, this, &Backend::onFramesReceived);
        connect(m_canDevice, &QCanBusDevice::framesWritten, this, &Backend::onFramesWritten);
    }

In my Backend.cpp ,
I tried this :

Backend::Backend(QObject *parent ) :QObject(parent), m_fetchFrameTimer(new QTimer(this))

{

[keskiverto]

// class definition
class Backend {

public:
  Backend( QObject *parent = nullptr ); // member declaration

};


// function definition (aka implementation)
Backend::Backend( QObject *parent )
 : QObject(parent), m_fetchFrameTimer(this)
{
  connect(&m_fetchFrameTimer, & QTimer::timeout, this, &Backend::fetchNextDataFrame);
  m_fetchFrameTimer.setSingleShot(true);

  m_canDevice = QCanBus::instance()->createDevice(QStringLiteral("socketcan"), QStringLiteral("can0"));
  connect(m_canDevice, &QCanBusDevice::framesReceived, this, &Backend::onFramesReceived);
  connect(m_canDevice, &QCanBusDevice::framesWritten, this, &Backend::onFramesWritten);
}