Connect to C++ signal from QML

[Rem-Kolomna]

Hi! I want to connect to C++ signals from QML like this:

action.onMouseUp = function() {
    console.log("mouse up>>");
}

And declare in my C++ object this signal:

signals:
  void mouseUp(const QPointF point);

But I'm getting QML Error: TypeError: Cannot assign to read-only property "mouseUp". What might the problem be?

[p3c0]

@Rem-Kolomna That is because you are trying to assign the function to that signal.
Use Connections instead.

Connections {
    target: action //if action is the target object
    onMouseUp: console.log(point)
}

[Rem-Kolomna]

Yeah, connection is a way to go, but I want to simplify qml code and write it like that:

action.onMouseUp = function()

It is one line instead of four lines))) May be I can use Q_QROPERTY(QJSValue...) for this task?

[p3c0]

@Rem-Kolomna You can't as mouseUp is a signal. You get something from signal and not give it.

[p3c0]

@Rem-Kolomna You can also use a connect method. Eg:

Component.onCompleted: {
    action.mouseUp.connect( function getPoint(myPoint) {console.log(myPoint) } );
}

[JKSH]

@Rem-Kolomna said:

action.onMouseUp = function() {
    console.log("mouse up>>");
}

Try replacing that with

action.onMouseUp: {
    console.log("mouse up>>");
}

@p3c0 said:

@Rem-Kolomna You can't as mouseUp is a signal. You get something from signal and not give it.

If mouseUp is the signal, then onMouseUp is the signal handler.

[p3c0]

@JKSH Right. I was just trying to explain that signals and the corresponding handlers cannot be assigned anything which produced that earlier error.

[Rem-Kolomna]

I found a simple solution for my problem. I just declare a property

Q_PROPERTY(QJSValue onMouseUp READ onMouseUp WRITE setOnMouseUp)

that I can call from C++ side as QJSValue::call(). It allows me to write more clean code and ensure to have a single signal handler for this event (it's also important for me)