Create attached properties in c++

NYBL

hello i am trying to create custom attached properties in c++ but it dosnt seem to work, here is the code:

// sidemenu.h
#include <QtCore>
#include <qqml.h>
#include <QtQuick/QQuickItem>

class SideMenuAttached : public QObject
{
    Q_OBJECT
    Q_PROPERTY(bool isCurrenPage READ isCurrenPage NOTIFY isCurrenPageChanged)
    QML_ANONYMOUS

public:
    using QObject::QObject;

    bool isCurrenPage() const;
    void setIsCurrenPage(bool newIsCurrenPage);

signals:
    void isCurrenPageChanged();

private:
    bool m_isCurrenPage = false;
};

class SideMenu : public QQuickItem
{
    Q_OBJECT
    Q_PROPERTY(int currentPage READ currentPage WRITE setCurrentPage NOTIFY currentPageChanged)
    QML_ELEMENT
    QML_ATTACHED(SideMenuAttached)

public:
    explicit SideMenu(QQuickItem *parent = nullptr);
    int currentPage() const;
    void setCurrentPage(int newCurrentPage);
    static SideMenuAttached *qmlAttachedProperties(QObject *);

signals:

    void currentPageChanged();

private:
    int m_currentPage;
};

//sidemenu.cpp
#include "sidemenu.h"

bool SideMenuAttached::isCurrenPage() const
{
    return m_isCurrenPage;
}

void SideMenuAttached::setIsCurrenPage(bool newIsCurrenPage)
{
    if (m_isCurrenPage == newIsCurrenPage)
        return;
    m_isCurrenPage = newIsCurrenPage;
    emit isCurrenPageChanged();
}


SideMenu::SideMenu(QQuickItem *parent)
    : QQuickItem(parent)
{
}

int SideMenu::currentPage() const
{
    return m_currentPage;
}

void SideMenu::setCurrentPage(int newCurrentPage)
{
    if (m_currentPage == newCurrentPage)
        return;
    m_currentPage = newCurrentPage;
    emit currentPageChanged();
}

SideMenuAttached *SideMenu::qmlAttachedProperties(QObject *object)
{
    return new SideMenuAttached(object);
}

// main.qml
import QtQuick
import components 1.0 as T

Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")
    Item{
        anchors.fill: parent;
        T.SideMenu{
            currentPage: 0;
            anchors.fill: parent;
            Rectangle{id: a;
                anchors.fill: parent;
                color: "grey"
                Component.onCompleted: {console.log("isCurrentPAge", a.SideMenu.isCurrenPage)}
            }

        }
    }
}

the error message i get is: TypeError: Cannot read property 'isCurrenPage' of undefined
what am i missing?

NYBL

i was suggested in dicord by @GrecKo to change:
Component.onCompleted: {console.log("isCurrentPAge", a.SideMenu.isCurrenPage)}
to:
Component.onCompleted: {console.log("isCurrentPAge", a.T.SideMenu.isCurrenPage)}

apparently the alias is not just for object instantiating..