// testmodel.h
#ifndef TESTMODEL_H
#define TESTMODEL_H

#include <QAbstractListModel>
#include <QJsonValue>

class TestModel : public QAbstractListModel
{
	Q_OBJECT
	QVariantList m_data;

public:
	TestModel(QObject *parent = nullptr) :
		QAbstractListModel(parent)
	{
		m_data = QVariantList{
			true,
			3.14159,
			"Hello",
			QJsonValue(true),
			QJsonValue(3.14159),
			QJsonValue("Hello")
		};
	}

	int rowCount(const QModelIndex&) const override
	{ return m_data.count(); }

	QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override
	{
		if (role == Qt::DisplayRole && index.row() >= 0 && index.row() < m_data.count())
			return m_data[index.row()];
		return QVariant();
	}
};

#endif // TESTMODEL_H

// main.cpp
#include "testmodel.h"
#include <QApplication>
#include <QListView>
#include <QDebug>

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

	TestModel model;
	for (int i = 0; i < model.rowCount(QModelIndex()); ++i)
		qDebug() << model.data(model.index(i));

	QListView view;
	view.setModel(&model);
	view.show();

	return a.exec();
}

QVariant(bool, true)
QVariant(double, 3.14159)
QVariant(QString, "Hello")
QVariant(QJsonValue, QJsonValue(bool, true))
QVariant(QJsonValue, QJsonValue(double, 3.14159))
QVariant(QJsonValue, QJsonValue(string, "Hello"))