How to hide C++ Slot in Qml / Private Slots - qt

Question

I don't want to expose a slot to QML, but is required to have a slot, because the slot is connected to internal signal.
I marked the slot as private, but the slots is accessible in QML e.g. Code completion/suggestion etc. My CPP Custom Class is registered in the main cpp.
h File:
#ifndef MYQMLTYPE_H
#define MYQMLTYPE_H
#include <QObject>
#include <QTimer>
class MyQMLType : public QObject
{
Q_OBJECT
Q_PROPERTY(QString message READ message WRITE setMessage NOTIFY messageChanged)
public:
explicit MyQMLType(QObject *parent = nullptr);
public slots:
int increment(int value);
private slots:
void hideslot(void);
signals:
void messageChanged();
public:
QString message() const;
void setMessage(const QString& value);
private:
QString m_message;
QTimer *m_timer;
};
#endif // MYQMLTYPE_H
Cpp File:
#include "myqmltype.h"
MyQMLType::MyQMLType(QObject *parent) : QObject(parent)
{
m_timer = new QTimer(this);
connect(m_timer, &QTimer::timeout, this, &MyQMLType::hideslot);
m_timer->start(1000);
}
int MyQMLType::increment(int value)
{
return value + 1;
}
void MyQMLType::hideslot()
{
// private slot
}
QString MyQMLType::message() const {
return m_message;
}
void MyQMLType::setMessage(const QString& value) {
if(m_message != value) {
m_message = value;
messageChanged(); // trigger signal of property change
}
}
Main.cpp:
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include "MyQMLType.h"
int main(int argc, char *argv[])
{
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QGuiApplication app(argc, argv);
qmlRegisterType<MyQMLType>("com.yourcompany.xyz", 1, 0, "MyQMLType");
QQmlApplicationEngine engine;
const QUrl url(QStringLiteral("qrc:/main.qml"));
QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
&app, [url](QObject *obj, const QUrl &objUrl) {
if (!obj && url == objUrl)
QCoreApplication::exit(-1);
}, Qt::QueuedConnection);
engine.load(url);
return app.exec();
}
main.qml:
import QtQuick 2.15
import QtQuick.Window 2.15
import com.yourcompany.xyz 1.0
Window {
width: 640
height: 480
visible: true
title: qsTr("Hello World")
MyQMLType{
id: myqmltype
}
Rectangle{
id: rect
anchors.centerIn: parent
width: 100
height: 100
color: myqmltype.hideslot(); // This slot is avaiable in qml
}
}
Question:
Why is the private slot exposed to QML?
How to hide the slot?
Edit
Optimized Cpp File with private slot

Answer 1

Your premise is wrong
I don't want to expose a slot to QML, but is required to have a slot, because the slot is connected to internal signal.
Using the new Qt 5 connect syntax with pointer to member function you don't need a function to be a slot to be able to connect to it.
Just put your hideslot declaration in the private section of your class and you'll have what you want. It won't be exposed to QML and you would still be able to connect to it in C++.
As to why the private slot is exposed to QML, it is because all slots and Q_INVOKABLE functions are exposed to QML, regardless of their access.