Unable to assign ... to QQmlComponent

patrick.gross

Hi guys,

i have the following qml file:

import QtQuick 2.0
import QtQuick.Controls 1.4

import "."

TableView {
    property string modelValue
    property var comboBoxModel
    id: tv

    TableViewColumn {
        role: "name"
        title: qsTr("Backtrace Data")
        width: (parent.width - 55) / 3

    }
    TableViewColumn {
        role: "description"
        title: qsTr("Description")
        width: (parent.width - 55) / 3
    }
    TableViewColumn {
        role: "value"
        title: qsTr("Value")
        width: (parent.width - 55) / 3

        delegate: myDelegate
    }

    rowDelegate: Rectangle {
        height: Style.table.rowHeight
        SystemPalette {
            id: myPalette;
            colorGroup: SystemPalette.Active
        }
        color: {
            var baseColor = styleData.alternate ? myPalette.alternateBase : myPalette.base
            return styleData.selected ? myPalette.highlight : baseColor
        }
    }

    itemDelegate: Item {
        Text {
            anchors.verticalCenter: parent.verticalCenter
            anchors.left: parent.left
            anchors.leftMargin: 5
            color: styleData.textColor
            elide: styleData.elideMode
            text: styleData.value
            font.pixelSize: Style.fontSize
        }
    }

    Component {
        id:  myDelegate
        Item {
            id: dummyItem
            Loader {
                sourceComponent: {
                    // can happen if the model has not loaded yet
                    if (model === null) {
                        return lineEdit;
                    }

                    if (model.componentType === "ComboBox") {
                        var cmb = Qt.createComponent("MyComboBox.qml").createObject(parent);
                        cmb.model = model.comboBoxModel;
                        cmb.anchors.fill = parent;
                        return cmb;
                    }else {
                        var le = Qt.createComponent("LineEdit.qml").createObject(parent);
                        le.anchors.fill = parent;
                        le.text = model.value;
                        //le.width = parent.width;
                        //le.height = parent.height;
                        return le;
                    }
                }
            }
        }
    }
}

I'm trying to dynamically create a Component based on the models componentType, which is currently just a Text or ComboBox. The creation works fine, but I always get warnings like: "Unable to assign ComboBox_QMLTYPE_86 to QQmlComponent"

Someone had a similar Problem here: https://forum.qt.io/topic/44314/reusing-a-delegate-component-in-qml
But simply wrapping my loader item in a Component doesn't seem to work for me.
Any ideas what im doing wrong?

patrick.gross

Ok, I got it. Drawing inspiration from this post, this is what I came up with:

import QtQuick 2.0
import QtQuick.Controls 1.4

TableView {
    ...
    
    TableViewColumn {
        id: compColumn
        role: "value"
        title: qsTr("Value")
        width: (parent.width - 55) / 3

        delegate:   Component {
            Loader {
                sourceComponent: {
                    // can happen if the model has not loaded yet
                    if (model === undefined || model === null || parent === null ) {
                        return;
                    }

                    return Qt.createQmlObject("import QtQuick 2.0;" +
                                               "Component {" +
                                               "Item { Component.onCompleted: loadComponent(this, model)}}", parent);
                }
            }
        }
    }

  // this function loads the actual component base on model.componentType
    function loadComponent(parent, model) {
        if (model === undefined || model === null) {
            console.log("model is null or undefined");
            return;
        }

        if (model.componentType === "ComboBox") {
            var cmb = Qt.createComponent("MyComboBox.qml").createObject(parent);
            cmb.model = model.comboBoxModel;
            cmb.anchors.fill = parent;
        } else if (model.componentType === "Text"){
            var txt = Qt.createQmlObject("import QtQuick 2.0;import QtQuick.Controls 1.4;TextInput{}", parent);
            txt.text = model.value;
            txt.anchors.left = parent.left;
            txt.anchors.leftMargin = 5;
            txt.anchors.verticalCenter = parent.verticalCenter;

        }
    }
}

Hope this can help out someone else in the future.

DamienL

Oooooh yes it helped ! Now I can generate my HMI components with different delegates depending on a specific property. Good for code efficiency and size !