how to disconnect the method for a signal in qml？

Question

In QML, in some situations, I need to remove the old method to a signal and redefine a new method to handle the signal, a demo is as following:

import QtQuick 2.6
import QtQuick.Window 2.2

Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    MouseArea {
        id:mouse
        anchors.fill: parent
        onClicked: {
            console.log("11111");
        }
    }


    Text {
        text: qsTr("Hello World")
        anchors.centerIn: parent
    }

    Component.onCompleted: {
        //if(false){
        //}
        // mouse.clicked = null;
        //mouse.clicked.disconnect();

        mouse.clicked.connect(
                    function(){
                        console.log("22222")
                    });
    }

}

I connect a new function, however it will show both "11111" and "22222", seems it add a new function to handle the signal.

I tried set "mouse.clicked = null", still doesn't work.

I also tried disconnect the method,like as following:

MouseArea {
    id:mouse
    anchors.fill: parent
    onClicked:say()
}

Component.onCompleted: {
    mouse.clicked.disconnect(say);
    mouse.clicked.connect(
                function(){
                    console.log("22222")
                });
}

function say(){
    console.log("11111");
}

Still print both "11111" and "22222", how can I remove the old methond and redefine the method in Component.onCompleted()?

update on 2017-6-13:

Thanks, guys.I also use connections,still cannot disconnect as I use qt5.6.1, there is no enable property :( . if we use explicitly connect() function, it works. but in my case, I think I can't connect a method , I need to check some If situations to define whether I need to remove the signal handler in Component.onCompleted.

Also a quick question, why the window component completed faster than mouseArea? the log "first load" first loaded.

  MouseArea {
        id:mouse
        anchors.fill: parent
        Connections{
            onClicked:say()
        }
        Component.onCompleted: {
            //mouse.clicked.connect(say)
            console.log("second load")
        }
    }

    Component.onCompleted: {
        console.log("first load")
        mouse.clicked.connect(
                    function(){
                        mouse.clicked.disconnect(say);
                        //mouse.clicked.disconnect(say);
                        console.log("22222")
                    });

    }

Answer 1

You can't disconnect the default signal handler onSignal: { do what ever }.

You can only dissconnect, when you have connected with onSignal.connect(say) beforehand. You could do this in Component.onCompleted.
If you use the syntax:

onSignal: say()

this equals

onSignal.connect(function() { say() })

and therefore you can't use onSignal.disconnect(say) as say was never connected. (I don't know whether it is connected to onSignal or to signal - both could be done manually, or whether it is not connected at all. You can't disconnect it, without having a reference to the implicitly created function.)

---

In QML, the nicer way would be to stay declarative. For this you can use the Connections-construct:

Connections {
    target: mouse // set to null to disconnect (Qt<=5.6)
    onClicked: { do what ever }
    enabled: true // change this, when you want to disconnect it (Qt>=5.7)
}