How to find a QML Context property with the property's name as a string in a QML file

Question

I have a model that is registered as a QML context property as so:

modelPtr = new MyModel();
engine_.rootContext()->setContextProperty(modelName, modelPtr);

In my QML files, rather than hardcode the modelName as a property binding like this:

ListView {
    model: modelName
} 

Is there a way I could search for the model I wanted by string name?

So far I have tried:

Item {
    property string modelName
    ListView {
         id: myListView
         Component.onCompleted: {
             myListView.model = Qt.binding(function() { return modelManager.getModel(modelName) } )
         }
    }
}

Where the modelManager contains all the models being used by the system (and is a registered context property) and the function "getModel" returns a QObject* to the desired model. This method did not seem to work with model updates.

Answer 1

It should work, but without seeing your model, it's hard to say what's going wrong. This works for me:

#include <QAbstractItemModel>
#include <QStandardItemModel>
#include <QApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>

class ModelManager : public QObject
{
    Q_OBJECT
public:
    ModelManager() {
        QStandardItemModel *model1 = new QStandardItemModel(4, 1, this);
        for (int row = 0; row < 4; ++row) {
            QStandardItem *item = new QStandardItem(QString("model1 row %0, column 0").arg(row));
            model1->setItem(row, 0, item);
        }
        mModels.insert("model1", model1);

        QStandardItemModel *model2 = new QStandardItemModel(4, 1, this);
        for (int row = 0; row < 4; ++row) {
            QStandardItem *item = new QStandardItem(QString("model2 row %0, column 0").arg(row));
            model2->setItem(row, 0, item);
        }
        mModels.insert("model2", model2);
    }

    Q_INVOKABLE QObject *getModel(const QString &modelName) {
        return mModels.value(modelName);
    }

    Q_INVOKABLE void changeStuff() {
        QStandardItemModel *model = static_cast<QStandardItemModel*>(mModels.value("model1"));
        QStandardItem *item = model->item(0, 0);
        item->setText("model1 row 0 column 0 - changed");
    }

private:
    QHash<QString, QAbstractItemModel*> mModels;
};

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    ModelManager modelManager;

    qRegisterMetaType<QAbstractItemModel*>();

    QQmlApplicationEngine engine;
    engine.rootContext()->setContextProperty("modelManager", &modelManager);
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    return app.exec();
}

#include "main.moc"

QML:

import QtQuick 2.4
import QtQuick.Controls 1.3
import QtQuick.Window 2.2
import QtQuick.Dialogs 1.2

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

    ComboBox {
        id: comboBox
        model: ["model1", "model2"]
    }

    ListView {
        id: listView
        width: 200
        height: 200
        anchors.centerIn: parent
        model: modelManager.getModel(comboBox.currentText)
        delegate: Rectangle {
            width: listView.width
            height: text.implicitHeight

            Text {
                id: text
                anchors.centerIn: parent
                text: display
            }
        }
    }

    Button {
        text: "Change stuff"
        anchors.horizontalCenter: listView.horizontalCenter
        onClicked: modelManager.changeStuff()
    }
}