Accessing item of QAbstractItemModel via Pointer gets NULL after several reads - qt

Question

I need to access items directly of an QAbstractListModel from QML.
I realized it by returning the address from a function from the model:
Function is
Q_INVOKABLE DataSourceObject *dataPointer(const QModelIndex &index);
#ifndef DATASOURCEMODEL_H
#define DATASOURCEMODEL_H
#include "datasourceobject.h"
#include <QAbstractListModel>
class DataSourceModel : public QAbstractListModel
{
Q_OBJECT
public:
enum datasourceRoles {
idRole = Qt::UserRole ,
nameRole,
unitRole,
valueRole
};
explicit DataSourceModel(QObject *parent = nullptr);
void addDataSourceObject(DataSourceObject *dataSourceObject);
Q_INVOKABLE QVariantMap get(int row) const;
int rowCount(const QModelIndex &parent = QModelIndex()) const override;
Q_INVOKABLE QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override;
bool setData(const QModelIndex &index, const QVariant &value,
int role = Qt::EditRole) override;
Q_INVOKABLE DataSourceObject *dataPointer(const QModelIndex &index);
Qt::ItemFlags flags(const QModelIndex& index) const override;
QHash<int, QByteArray> roleNames() const override;
//bool checkIndex(const QModelIndex &index) const;
private:
QList<DataSourceObject*> m_DataSourceObjects;
};
#endif // DATASOURCEMODEL_H
#include "datasourcemodel.h"
#include <qdebug.h>
DataSourceModel::DataSourceModel(QObject *parent)
: QAbstractListModel(parent)
{
}
QVariantMap DataSourceModel::get(int row) const
{
return m_DataSourceObjects[row]->toMap();
}
void DataSourceModel::addDataSourceObject(DataSourceObject *dataSourceObject)
{
beginInsertRows(QModelIndex(), rowCount(), rowCount());
m_DataSourceObjects << dataSourceObject;
endInsertRows();
}
int DataSourceModel::rowCount(const QModelIndex &parent) const
{
if (parent.isValid())
return 0;
return m_DataSourceObjects.count();
}
QVariant DataSourceModel::data(const QModelIndex &index, int role) const
{
if(index.row() < 0 || index.row() >= m_DataSourceObjects.count() || !index.isValid())
return QVariant();
DataSourceObject *dataSourceObject = m_DataSourceObjects[index.row()];
if (role == idRole)
return dataSourceObject->id();
else if (role == nameRole) {
return dataSourceObject->name();
}
else if (role == unitRole) {
return dataSourceObject->unit();
}
else if (role == valueRole)
return dataSourceObject->value();
return QVariant();
}
bool DataSourceModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
DataSourceObject *dataSourceObject = m_DataSourceObjects[index.row()];
if (data(index, role) != value) {
if(role == idRole)
dataSourceObject->setId(value.toInt());
else if(role == nameRole)
dataSourceObject->setName(value.toString());
else if(role == unitRole)
dataSourceObject->setUnit(value.toString());
else if(role == valueRole)
dataSourceObject->setValue(value.toDouble());
emit dataChanged(index, index, QVector<int>() << role);
return true;
}
return false;
}
DataSourceObject *DataSourceModel::dataPointer(const QModelIndex &index)
{
qDebug() << m_DataSourceObjects[index.row()];
return m_DataSourceObjects[index.row()];
}
Qt::ItemFlags DataSourceModel::flags(const QModelIndex &index) const
{
if (!index.isValid())
return Qt::NoItemFlags;
return Qt::ItemIsEditable; // FIXME: Implement me!
}
QHash<int, QByteArray> DataSourceModel::roleNames() const
{
QHash<int, QByteArray> roles;
roles[idRole] = "id";
roles[nameRole] = "name";
roles[unitRole] = "unit";
roles[valueRole] = "value";
return roles;
}
I can access the item and it's propertys from QML and the GUI gets automatically updated with Q_PROPERTY on the gui.
text: dataSourceModel.dataPointer(dataSourceModel.index(88,0)).value
Object:
#ifndef DATASOURCEOBJECT_H
#define DATASOURCEOBJECT_H
#include <QString>
#include <QVariantMap>
class DataSourceObject : public QObject
{
Q_OBJECT
Q_PROPERTY(double value READ value WRITE setValue NOTIFY valueChanged)
public:
explicit DataSourceObject(QObject *parent = nullptr);
DataSourceObject(const QJsonObject &obj);
int id() const;
void setId(int id);
QString name() const;
void setName(const QString &name);
QString unit() const;
void setUnit(const QString &unit);
Q_INVOKABLE double value() const;
void setValue(double value);
QVariantMap toMap() const;
signals:
void valueChanged();
private:
int m_id;
QString m_name;
QString m_unit;
double m_value;
};
#endif // DATASOURCEOBJECT_H
The property "value" of the items get's changed during runtime in background.
After circa 80 changes of the propertys the pointer that points to the object returns NULL. So I assume the item in the model changed it's address.
How can I prevent the model to change the addresses of it's item.
But also when I call again Q_INVOKABLE DataSourceObject *dataPointer(const QModelIndex &index); to get the address again, the "old" address ist returned but a "QObject" instead of "DataSourceObject"