Problem with model, or Instantiator

[fcarney]

I have a QAbstractListModel with some methods that I think are correct:

void JsonObjectStore::insert(int ind, QJSValue jsondata)
{
    if(ind < 0 || ind > rowCount())
        return;

    auto pjsondata = prepareData(jsondata);
    if(!pjsondata)
        return;

    QAbstractListModel::beginInsertRows(index(ind,0), ind, ind);
    m_jsonObjectList.insert(ind, pjsondata);
    QAbstractListModel::endInsertRows();

    emit countChanged();
}

void JsonObjectStore::remove(int ind, int n)
{
    if(ind < 0 || (ind + n) > rowCount()){
        qDebug() << "JsonObjectStore::remove index+count too big:" << ind << n << rowCount();
        return;
    }

    QAbstractListModel::beginRemoveRows(index(ind,0), ind, ind+(n-1));
    for(int count=ind; count < ind+n && count < m_jsonObjectList.size(); ++count)
        delete m_jsonObjectList[count];
    m_jsonObjectList.remove(ind, n); // does this return an error/crash if extends past list end?
    QAbstractListModel::endRemoveRows();

    emit countChanged();
}

Insert seems to trigger the down stream Instantiator just fine, but I am not seeing the Instantiator call onObjectRemoved. I originally assumed it was the remove method at fault, but I cannot tell what is wrong with it.

            Instantiator {
                id: editor_repeater

                active: true
                model: loaded_objects

                property var grid_object: edit_grid_board
                property int currentIndex: -1

                delegate: EditorObject {
                    id: etdelegate

                    params: datarole
                    inst_index: index

                    width: editor_repeater.grid_object.cell_width * gw
                    height: editor_repeater.grid_object.cell_height * gh

                    anchors.left: parent.left
                    anchors.top: parent.top
                    clip: true

                    selected: editor_repeater.currentIndex === index

                    onDroppedObject: {
                        if(dropobj.drop.keys.includes("pathkey")){
                            loaded_objects.setProperty(index, inst_obj.dropProperties.path, dropobj.drop.source.dropdata.path.toString())
                            loaded_objects.dirty = true
                        }
                    }

                    MouseArea {
                        id: etdelegate_mousearea

                        anchors.fill: parent
                        acceptedButtons: Qt.LeftButton | Qt.RightButton

                        onClicked: {
                            //console.log("clicked")
                            if(mouse.button === Qt.LeftButton){
                                editor_repeater.currentIndex = index
                            }else if(mouse.button === Qt.RightButton){
                                etdelegate_contextmenu.popup()
                            }
                        }
                    }

                    Menu {
                        id: etdelegate_contextmenu

                        MenuItem {
                            text: "Delete"
                            onTriggered: {
                                editor_repeater.model.remove(index)
                            }
                        }
                    }
                }

                onObjectAdded: {
                    var pos_object = grid_object.getDelegateInsertObject(object.gx, object.gy)
                    pos_object.data.push(object)
                }
                onObjectRemoved: {
                    console.log(object)
                }
            }

There is a bunch of junk in Instantiator, but you get the idea. The object does not seem to dissapear like I thought it would. When I right click to call remove again I get the warning about it being out of bounds. So it is not in the QVector m_jsonObjectList anymore. I don't understand why it is not seeing the beginRemoveRows and endRemoveRows.

[fcarney]

Here is a better example:

#ifndef CUSTOMMODEL_H
#define CUSTOMMODEL_H

#include <QObject>
#include <QAbstractListModel>

class BasicModel : public QAbstractListModel
{
    Q_OBJECT
    Q_PROPERTY(int count READ rowCount NOTIFY countChanged)

    int m_count;
    QVector<int> m_list;

public:
    BasicModel(QObject* parent=nullptr)
        : QAbstractListModel(parent)
    {
    }

    int rowCount(const QModelIndex &parent = QModelIndex()) const{
        return m_list.count();
    }
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const{
        if(index.row() < 0 || index.row() >= rowCount())
            return QVariant();

        if(role != Qt::DisplayRole)
            return QVariant();

        return m_list[index.row()];
    }
signals:
    void countChanged();

public slots:
    void insert(int ind, int data){
        if(ind < 0 || ind > rowCount())
            return;

        QAbstractListModel::beginInsertRows(index(ind,0), ind, ind);
        m_list.insert(ind, data);
        QAbstractListModel::endInsertRows();

        emit countChanged();
    }
    void remove(int ind){
        if(ind < 0 || ind >= rowCount())
            return;

        QAbstractListModel::beginRemoveRows(index(ind,0), ind, ind);
        m_list.remove(ind);
        QAbstractListModel::endRemoveRows();

        emit countChanged();
    }
};

#endif // CUSTOMMODEL_H

main.cpp:

#include <QGuiApplication>
#include <QQmlApplicationEngine>

#include "custommodel.h"

int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);

    QGuiApplication app(argc, argv);

    qmlRegisterType<BasicModel>("BasicModels",1,0,"BasicModel");

    QQmlApplicationEngine engine;
    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                     &app, [url](QObject *obj, const QUrl &objUrl) {
        if (!obj && url == objUrl)
            QCoreApplication::exit(-1);
    }, Qt::QueuedConnection);
    engine.load(url);

    return app.exec();
}

main.qml:

import QtQuick 2.15
import QtQuick.Window 2.15
import QtQml.Models 2.15

import BasicModels 1.0

Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("Test Instantiator Custom Model")

    BasicModel {
        id: basicmodel
    }

    ListModel {
        id: objectmodel
    }

    Instantiator {
        id: instantiator

        model: basicmodel

        delegate: Text {
            text: display
        }

        onObjectAdded: {
            console.log("onObjectAdded", object.text)
        }
        onObjectRemoved: {
            console.log("onObjectRemoved", object.text)
        }

        Component.onCompleted: {
            instantiator.model.insert(instantiator.model.count, 1)
            instantiator.model.insert(instantiator.model.count, 2)
            console.log(instantiator.model.count)

            Qt.callLater(removeItems)
        }

        function removeItems(){
            while(instantiator.model.count){
                instantiator.model.remove(0)
            }
            console.log(instantiator.model.count)
        }
    }
}

It calls the onObjectRemoved on the ListModel, but not on the BasicModel. I thought ListModel was based on QAbstractListModel, so I don't know what the issue is.

[fcarney]

This better illustrates the issue:

import QtQuick 2.15
import QtQuick.Window 2.15
import QtQml.Models 2.15

import BasicModels 1.0

Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("Test Instantiator Custom Model")

    BasicModel {
        id: basicmodel
    }

    ListModel {
        id: objectmodel
    }

    Instantiator {
        id: instantiator

        model: basicmodel

        delegate: Text {
            text: display
        }

        onObjectAdded: {
            console.log("onObjectAdded", object.text)
        }
        onObjectRemoved: {
            console.log("onObjectRemoved", object.text)
        }

        Component.onCompleted: {
            console.log("instantiator")
            instantiator.model.insert(instantiator.model.count, 1)
            instantiator.model.insert(instantiator.model.count, 2)
            console.log(instantiator.model.count)

            Qt.callLater(removeItems)
        }

        function removeItems(){
            console.log("instantiator")
            while(instantiator.model.count){
                instantiator.model.remove(0)
            }
            console.log(instantiator.model.count)
        }
    }

    Instantiator {
        id: instantiator2

        model: objectmodel

        delegate: Text {
            text: display
        }

        onObjectAdded: {
            console.log("onObjectAdded", object.text)
        }
        onObjectRemoved: {
            console.log("onObjectRemoved", object.text)
        }

        Component.onCompleted: {
            console.log("instantiator2")
            instantiator2.model.insert(instantiator.model.count, {display:1})
            instantiator2.model.insert(instantiator.model.count, {display:2})
            console.log(instantiator2.model.count)

            Qt.callLater(removeItems)
        }

        function removeItems(){
            console.log("instantiator2")
            while(instantiator2.model.count){
                instantiator2.model.remove(0)
            }
            console.log(instantiator2.model.count)
        }
    }
}

[fcarney]

Okay, stupid mistake:

void insert(int ind, int data){
        if(ind < 0 || ind > rowCount())
            return;

        QAbstractListModel::beginInsertRows(QModelIndex(), ind, ind);
        m_list.insert(ind, data);
        QAbstractListModel::endInsertRows();

        emit countChanged();
    }
    void remove(int ind){
        if(ind < 0 || ind >= rowCount())
            return;

        QAbstractListModel::beginRemoveRows(QModelIndex(), ind, ind);
        m_list.remove(ind);
        QAbstractListModel::endRemoveRows();

        emit countChanged();
    }