How to delete data from the QML treeview model?

Question

Based on the QML example treeview given by Qt, how does one clear an entire tree model without destroying the model? Essentially, I want to wipe all of the items/elements from the tree, without destroying the tree itself. The specific code I am using was donated by eyllanesc.

I modified the original code to make *elementFromIndex(...) as Q_INVOKABLE

Within QML, I tried:

elementFromIndex(treemodel.index(0,0))->clear();
elementFromIndex(-1)->clear();

and then realized that QML doesn't understand pointers. So I'm sort of at a loss because of the logic of the tree. I know I essentially need to call something like: myRootItem.clear() but I don't know how to reference the identity of myRootItem. There is not a clear() function within the TreeModel itself, only the TreeElement object.

Complete code example here

TreeElement.h

class TreeElement : public QObject
{
    Q_OBJECT
public:
    Q_PROPERTY(QQmlListProperty<TreeElement> items READ items)
    Q_CLASSINFO("DefaultProperty", "items")
    TreeElement(QObject *parent = Q_NULLPTR);

    Q_INVOKABLE TreeElement *parentItem() const;
    bool insertItem(TreeElement *item, int pos = -1);
    QQmlListProperty<TreeElement> items();

    TreeElement *child(int index) const;
    void clear();

    Q_INVOKABLE int pos() const;
    Q_INVOKABLE int count() const;

private:
    static void appendElement(QQmlListProperty<TreeElement> *property, TreeElement *value);
    static int countElement(QQmlListProperty<TreeElement> *property);
    static void clearElement(QQmlListProperty<TreeElement> *property);
    static TreeElement *atElement(QQmlListProperty<TreeElement> *property, int index);

    QList<TreeElement *> m_childs;
    TreeElement *m_parent;
};

TreeModel.h

class TreeModel : public QAbstractItemModel
{
    Q_OBJECT
public:
    Q_PROPERTY(QQmlListProperty<TreeElement> items READ items)
    Q_PROPERTY(QVariantList roles READ roles WRITE setRoles NOTIFY rolesChanged)
    Q_CLASSINFO("DefaultProperty", "items")

    TreeModel(QObject *parent = Q_NULLPTR);
    ~TreeModel() override;

    QHash<int, QByteArray> roleNames() const Q_DECL_OVERRIDE;
    QVariant data(const QModelIndex &index, int role) const Q_DECL_OVERRIDE;
    Qt::ItemFlags flags(const QModelIndex &index) const Q_DECL_OVERRIDE;
    QModelIndex index(int row, int column, const QModelIndex &parent = QModelIndex()) const Q_DECL_OVERRIDE;
    QModelIndex parent(const QModelIndex &index) const Q_DECL_OVERRIDE;
    int rowCount(const QModelIndex &parent = QModelIndex()) const Q_DECL_OVERRIDE;
    int columnCount(const QModelIndex &parent = QModelIndex()) const Q_DECL_OVERRIDE;
    QQmlListProperty<TreeElement> items();

    QVariantList roles() const;
    void setRoles(const QVariantList &roles);

    Q_INVOKABLE QModelIndex indexFromElement(TreeElement *item);
    Q_INVOKABLE bool insertElement(TreeElement *item, const QModelIndex &parent = QModelIndex(), int pos = -1);

    TreeElement *elementFromIndex(const QModelIndex &index) const;

private:
    TreeElement *m_root;
    QHash<int, QByteArray> m_roles;

signals:
    void rolesChanged();
};