Can an onClicked() be a property?

[piervalli]

@mzimmers

QHash<int,QByteArray> roleNames() //mandatory for qml
int rowCount

Example
https://stackoverflow.com/questions/44777999/manipulate-data-in-a-qabstractlistmodel-from-a-qml-listview

[fcarney]

@mzimmers

// Roundlist.qml
Rectangle { // list background
    property alias model: listView.model

    signal doClick(ind index)

    Component {
        id: listDelegate
        Rectangle {
            ...
            MouseArea {
                onClicked: { doClick(index) }
            }
        }
    }
    ListView {
        id: listView
        delegate: listDelegate
    }
}

Then use:

ListModel {
    id: zoneDetailModel
    ListElement { parameter: "text1"; value: "value1"; funcIndex: 0}
    ListElement { parameter: "text2"; value: "value2"; funcIndex: 1}
    ListElement { parameter: "text3"; value: "value3"; funcIndex: 2}
}

property var funcs: [
  function(){ //do stuff},
  function(){ //do stuff},
  function(){ //do stuff},
]

Roundlist {
    model: zoneNameModel

   onDoClick: {
      funcs[index]()
   }
}

You could also pass a parameter if you really want via the signal.
You cannot put a function like this in your model. That won't work with ListModel. You have to have a separate structure to point to the function. You could define your functions outside the list as well and reference by name.

[mzimmers]

@fcarney very understandable; thanks. A couple questions:

1. instead ofthe explicit funcIndex values, can the call to doClick() somehow extract the index of the zoneDetailModel? That would make the implementation just a bit cleaner.
2. If my "do stuff" is just to display a new screen, or produce a popup, how do I proceduralize that?

Thanks...this is really helpful.

[fcarney]

@mzimmers Yeah, I started that thought, but didn't finish. Should be able to use the funcIndex from the model instead of the model index that is implied.

So you could call doClick(funcIndex) instead.

[fcarney]

@mzimmers said in Can an onClicked() be a property?:

If my "do stuff" is just to display a new screen, or produce a popup, how do I proceduralize that?

I would use a state for that. There are all kinds of state things that can call functions and set properties on things. That is how we do dialog boxes is with states.

[GrecKo]

If the list is static it doesn't need to be a ListModel, you could then have a function directly in the model:

ListView {
    model: [
        { parameter: "text1", value: "value1", action: ()  => { doStuf(1) }},
        { parameter: "text2", value: "value2", action: ()  => { doStuf(2) }},
        { parameter: "text3", value: "value3", action: ()  => { doStuf(3) }}
    ]
    delegate: Item {
        // ...
        TapHandler {
            onTapped: modelData.action()
        }
    }

}

[mzimmers]

@GrecKo @fcarney thanks for the suggestions. As I mentioned above, eventually this model will be defined in C++, so I'm not sure whether QML will view it as static, but at least i can use @fcarney's suggestion.

[mzimmers]

@fcarney I implemented your suggestion like so:

ListModel {
    id: zoneDetailModel
    ListElement { parameter: "param0"; value: "value0"; funcIndex: 0 }
    ListElement { parameter: "param1"; value: "value1"; funcIndex: 1  }
    ListElement { parameter: "param2"; value: "value2"; funcIndex: 2  }
}

property var funcs: [
    function() { console.log("0!") },
    function() { console.log("1!") },
    function() { console.log("2!") },
]
Roundlist {
    id: detailList
    width: newZone.width - (scroller.width * 2)
    model: zoneDetailModel
    onDoClick: {
        funcs[index]()
    }
}

It seems to work, though the first time I click on one of the items, I get this:

qt.qml.context: qrc:/nga_demo/Newzone.qml:68:13 Parameter "index" is not declared. Injection of parameters into signal handlers is deprecated. Use JavaScript functions with formal parameters instead.

Is this something that can be dealt with?

BTW: I believe that this line:

signal doClick(ind index)

should be:

signal doClick(int index)

yes?

Thanks...

[fcarney]

@mzimmers said in Can an onClicked() be a property?:

Injection of parameters into signal handlers is deprecated.

That is Qt 6 issue:
https://forum.qt.io/topic/139189/keystrokes-parameter-event-is-not-declared-injection-of-parameters-into-signal-handlers-is-deprecated-use-javascript-functions-with-formal-parameters-instead

I searched on "Injection of parameters into signal handlers is deprecated."

[mzimmers]

@fcarney ah yes, my old friend the lambda.

Roundlist {
    id: detailList
    width: newZone.width - (scroller.width * 2)
    model: zoneDetailModel
    onDoClick: (index)=> {
                   funcs[index]()
               }
}

This eliminated the error, and works fine.

Lambdas still look weird to me, though...

Thanks for the help.