C++ signal is emitted only once, but the QML slot is executed multiple times (Qt 5.15.5).

[Alexuds79]

Hi. I am trying to make a simple connection between C++ and QML through signals and slots. Everything works correctly except for one thing:

I have the C++ signal, which is emitted like this:

emit mySignal();

And in my test.qml file, I have the corresponding slot:

Connections{
    target: mainWindow

     function onMySignal(){
        console.log("Signal received");
    }
}

This whole process is handled automatically by the QML engine.

When the signal is first emitted, the operation is correct: "Signal received" appears once. However, when I emit the signal more times, the number of slot executions increases for each time the signal is emitted, ie:

First emit: slot is executed once.
Second emit: slot is executed twice.
Third emit: slot is executed three times.
And so on.

The desired behaviour would be that, each time I make an emit, the slot is executed only once. How can I achieve this?

Thanks in advance.

[Alexuds79]

@SGaist Thanks again for your reply, it really gave me the key to know what was going on. The problem was that the Connections were defined in a component that was continuously being created and destroyed, as it is part of a StackView. With this behaviour, every time the component was created, a new connection was defined. Moving the connections to a general component solves the problem.

Thank you very much! :)

[SGaist]

Hi,

It means that you are connecting the signal more than once. Check your code for that.

[Alexuds79]

@SGaist Thank you for your response. In fact, I am not making any connect because this part is already handled by the QML engine. Is it possible to somehow get the QML engine not to create a new connection every time an emit is made?

[SGaist]

émit does not create any new connection. The slot is called because the connection was created.

Ensure that you don't have multiple objects created that are connected to your C++ object.

[Alexuds79]

@SGaist Thanks again for your reply, it really gave me the key to know what was going on. The problem was that the Connections were defined in a component that was continuously being created and destroyed, as it is part of a StackView. With this behaviour, every time the component was created, a new connection was defined. Moving the connections to a general component solves the problem.

Thank you very much! :)