Close connection qobject

BjornW

When connecting to a lambda, you need to save the returned QMetaObject::Connection. From the docs:

QMetaObject::Connection QObject::connect(const QObject *sender, PointerToMemberFunction signal, Functor functor)

So something like.... (Can't compile right now)

void MainWindow::escucharMouse()
{
      auto connection = QObject::connect(&mouselog::instance(), &mouselog::mouseEvent, [](){ });
      ...
      QObject::disconnect(connection);      
}

EDIT: By "need to save" I mean that if you wish to disconnect a connection, you need to save the return value. If you're not going to, just leave it!

Jeronimo

@BjornW ok

BjornW

If you want to disconnect elsewhere you need to save the connection object inside your class.

Again, I did not compile this. But it should give you an idea.

class MainWindow : public QMainWindow
{
...
private:
   QMetaObject::Connection m_connection;
};

...

void MainWindow::escucharMouse()
{
      m_connection = QObject::connect(&mouselog::instance(), &mouselog::mouseEvent, [](){ });
}
void MainWindow::stopEscucharMouse()
{
      QObject::disconnect(m_connection ); 
}

On a side note, today I learned that escuchar means listen. Which reminded me of the song "Equador" (by Sash) where they sing "Escuchame". Funny how things connect. And disconnect :).

Jeronimo

@BjornW said in Close connection qobject:

m_connection

thx a lot!!

BjornW

Good luck :)

Jeronimo

@BjornW your help me a lot thx but i think when someone use one hook for mouse events for example it's impossible to close this connection. thx again!

BjornW

Post your code please. I don't understand. It should always be possible to close the connection.

Jeronimo

@BjornW maybe can be because in my main window class i defined with this way
class MainWindow : public QObject {

}???

mrjj

@Jeronimo
Actually all QWidgets are QObject too so it should not matter.

BjornW

Do you inherit QMainWindow?

class MainWindow : public QMainWindow

Jeronimo

@BjornW i only did one function to connect:
void MainWindow::escucharMouse()
{
m_connection = QObject::connect(&mouselog::instance(), &mouselog::mouseEvent, { });
}
Other for close:
void MainWindow::stopEscucharMouse()
{
QObject::disconnect(m_connection );
}
i defined in headers:
class MainWindow : public QMainWindow
{
...
public
private:
QMetaObject::Connection m_connection;
public slots:
void escucharMouse();
void apagarMouse();
and slots to call these functions (two buttons)
};

and in the slots i call the function one to open other to close like:

void MainWindow::slot1(){
m_connection = QObject::connect(&mouselog::instance(), &mouselog::mouseEvent, { });
}

void MainWindow::slot1(){
QObject::disconnect(m_connection );
}
i'm using one hook to capture the events of my mouse.
seems not to close connection and still capture events.

BjornW

You have two definitions of slot1()?

Jeronimo

@BjornW i tried two different public slots like:

connect(&this->verMouse,SIGNAL(timeout()),this,SLOT(escucharMouse()));
connect(&this->verMouse,SIGNAL(timeout()),this,SLOT(stopEscucharMouse()));

void MainWindow::escucharMouse()
{
      m_connection = QObject::connect(&mouselog::instance(), &mouselog::mouseEvent, [](){ });
}
void MainWindow::stopEscucharMouse()
{
      QObject::disconnect(m_connection ); 
}

with headers in private for metaobject::connection and slots in public slots.

But now how can call one slot or other i call them for example with this way:

escucharMouse(); -> to connect
stopEscucharMouse(); -> dont listen more

I put two different slots

Works to connect but to disconnect not seems to work.
inherit of qobject

Jeronimo

i solved my problem but the connection still thx all

BjornW

This does not seem right:

connect(&this->verMouse,SIGNAL(timeout()),this,SLOT(escucharMouse()));
connect(&this->verMouse,SIGNAL(timeout()),this,SLOT(stopEscucharMouse()));

You connect the same signal. And why does "verMouse" have a a timeout? What is it?

Anyway, since you say you solved your problem...

Jeronimo

@BjornW i need to use different signals to close the connection? i put timeout because these slots will repeat each time i say. I'm interesting to solve this issue because it's very useful too.

Jeronimo

@BjornW verMouse.setInterval(50); with this i was trying to stop the signal verMouse.stop() documentation https://doc.qt.io/qt-4.8/qtimer.html#stop

BjornW

connect(&this->verMouse,SIGNAL(timeout()),this,SLOT(escucharMouse()));
connect(&this->verMouse,SIGNAL(timeout()),this,SLOT(stopEscucharMouse()));

You have connected the same signal to both escuchar/stopEscuchar! This makes no sense. The order in which the slots are called is undefined in this case.