spinBox value is unbind

Idodoqdo

I have bind the model value to speenBox

        SpinBox {
           id: spinbox
           Layout.preferredWidth: parent.width * 0.3

           from: 0
           value: val
           to: 100

           validator: DoubleValidator {
               bottom: Math.min(spinbox.from, spinbox.to)
               top:  Math.max(spinbox.from, spinbox.to)
           }

           onValueChanged: {
             val = value
           }
        }

A loop appeared, but I prevented it as follows:

bool CameraConfigurationSettingsModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
    int row = index.row();

    if (row < 0 || row >= settings_.count()) {
        return false;
    }

    CameraConfigurationSetting& setting = settings_[row];

    switch (role) {
        case valueRole:
            if (setting.GetValue() == value.toDouble()) { // here
                return false;
            }
            setting.SetValue(value.toDouble());
            emit dataChanged(index, index);
            return true;
        case switchedRole:
            setting.Switch();
            emit dataChanged(index, index);
            return true;
    }

    return false;
}

By changing the value in SpeenBox using the up and down arrows, changing the value does not affect the binding, but if I write a value in the field, then after that it will be unlinked. help me please

sierdzio

@Idodoqdo this is a standard problem in QML stemming from a conflict between declarative and imperative ways of operation and there are a few ways around it.

One is to use a 2-way binding, see for example this presentation from KDAB about it: link.

Another would be to not set the binding at all, but rather react in slots to both onValueChanged (when user changes the value) and onValChanged (when the model is updated).

Idodoqdo

@sierdzio and how will the display understand that the changes relate specifically to this model? Can you please suggest sources that will help me do the 2nd method?

sierdzio

@Idodoqdo said in speenBox value is unbind:

@sierdzio and how will the display understand that the changes relate specifically to this model? Can you please suggest sources that will help me do the 2nd method?

You will set value in the slots, so it will be updated in the UI right away.

Idodoqdo

@sierdzio I'm new to qml, so I don't know how to do onValChanged

Idodoqdo

@sierdzio

how to make Connections if I don't have a model in the component. Only roles?

Item {
    id:cell

    RowLayout {
        spacing: 0
        anchors.fill: parent
        Rectangle {
            border.color: "black"
            color: "black"
            Layout.preferredWidth: parent.width * 0.2
            Layout.fillHeight: true
            Switch {
                checked: switched
                anchors.centerIn: parent
                visible: isHaveSwitch
                Layout.alignment: Qt.AlignHCenter | Qt.AlignVCenter
                onClicked: {
                    switched = !switched
                }

            }
        }
        Rectangle {
            color: "black"
            Layout.fillWidth:  true
            Layout.fillHeight: true
            Text {
                font.bold: true
                color: "white"
                text: name
                anchors.left: parent.left
                anchors.verticalCenter: parent.verticalCenter

            }
        }

        SpinBox {
           id: spinbox
           Layout.preferredWidth: parent.width * 0.3

           from: 0
           value: val
           to: 100

           validator: DoubleValidator {
               bottom: Math.min(spinbox.from, spinbox.to)
               top:  Math.max(spinbox.from, spinbox.to)
           }

           onValueChanged: {
             val = value
           }

        }
    }
}

sierdzio

@Idodoqdo that is a very good question. You can emit a signal in the model and then make Connections to the model itself.
Or you can return a QObject from your model (in one of the roles) and have your signal there (and connect to it).

Idodoqdo

@sierdzio
in the 2nd case, should the elements of my QAbstractListModel be inherited from QObject?If these are ordinary objects, then only in the first way. Thanks

sierdzio

@Idodoqdo said in spinBox value is unbind:

@sierdzio
in the 2nd case, should the elements of my QAbstractListModel be inherited from QObject?If these are ordinary objects, then only in the first way. Thanks

Yes, either Q_OBJECT or Q_GADGET, only such objects are visible to QML.

Well ok technically you can return a QVariantMap, too and it "looks" like an object in QML, but it is a hacky solution.

GrecKo

All that shouldn't be needed, SpinBox already supports not breaking bindings:

ListModel {
        id: listModel
        ListElement {
            val: 12
        }
        ListElement {
            val: 33
        }
    }

    Row {
        anchors.centerIn: parent
        spacing: 10
        Repeater {
            model: 2
            Column {
                Repeater {
                    model: listModel
                    SpinBox {
                        id: spinbox
                        editable: true
                        from: 0
                        to: 50
                        value: val
                        onValueModified: val = value
                        validator: DoubleValidator {
                            bottom: Math.min(spinbox.from, spinbox.to)
                            top:  Math.max(spinbox.from, spinbox.to)
                        }
                    }
                }
            }
        }
    }

Prefer using the interaction signal valueModified than the raw signal valueChanged to only catch changes from user interactions and not those from backend bindings like the loop you had before.

Idodoqdo

@GrecKo Thank you. I will try