QML: How to call method from a C++ subclass? - c++

Question

I have two C++ classes (TrafficLight and Light). Light is a child of TrafficLight. QML can see everything from TrafficLight and nothing from Light, for example...I get the following error when I try to access a method from Light like TrafficLight.get_light(0).get_color()
TypeError: Cannot call method 'get_color' of undefined
I exposed my parent class (TrafficLight) to qml (see main below). I assumed it would expose the subclass inside it, as well...but apparently not.
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include "traffic_light.h"
int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
QQmlApplicationEngine engine;
Traffic_Light traffic_light;
engine.rootContext()->setContextProperty("TrafficLight", &traffic_light);
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
return app.exec();
}
My question is how would I expose the subclass? I can't just create an instance of Light and expose it the same way I did TrafficLight. Reason being is it won't be the same Light that's inside the TrafficLight. :(
light.h
#ifndef LIGHT_H
#define LIGHT_H
#include <QDebug>
#include <QObject>
enum Color
{
RED = 0,
YELLOW,
GREEN
};
class Light : public QObject{
Q_OBJECT
public:
Light();
public slots:
void set_color(Color color);
int get_color();
void set_light(bool is_on);
bool get_light();
private:
Color m_color;
bool m_light_on;
};
#endif // LIGHT_H
traffic_light.h
#ifndef TRAFFIC_LIGHT_H
#define TRAFFIC_LIGHT_H
#include <QDebug>
#include <QObject>
#include <QTimer>
#include "light.h"
class Traffic_Light : public QObject
{
Q_OBJECT
public:
Traffic_Light();
public slots:
Light &get_light(int index);
void toggle_light(int index);
private:
Light m_light[3];
};
#endif // TRAFFIC_LIGHT_H