Accessing QObject class properties which is stored in QList

pra7

Hello, I am having trouble in accessing a property in QML.

QList<ClassB> is a property and i am able to access that but when i try to access the properties of classB in QML i am getting type error/Undefined. Following is the code:

//ClassA.h

#include <QObject>
#include "classb.h"

Q_DECLARE_METATYPE(QList<ClassB*>)
class ClassA : public QObject
{
    Q_OBJECT
    Q_PROPERTY(QList<ClassB*> objList READ getClassBDetails)

public:
    explicit ClassA(QObject *parent = nullptr);

    QList<ClassB *>getClassBDetails();

private:
    QList<ClassB*> m_list;
    ClassB m_Bobj;

};

//ClassA.cpp

#include "classa.h"

ClassA::ClassA(QObject *parent) : QObject(parent)
{
    m_list.append(&m_Bobj);
}

QList<ClassB *> ClassA ::getClassBDetails()
{
    return m_list;
}

//ClassB.h

#include <QObject>

class ClassB : public QObject
{
    Q_OBJECT
    Q_PROPERTY(int val READ getval WRITE setval NOTIFY valChanged)
public:
    explicit ClassB(QObject *parent = nullptr);

    int m_val = 10;

    int getval();
    void setval(int val);

signals:
    void valChanged();

public slots:
};

//ClassB.cpp

#include "classb.h"
ClassB::ClassB(QObject *parent) : QObject(parent)
{

}

int ClassB::getval()
{
    return m_val;
}

void ClassB::setval(int val)
{
    m_val = val;
    emit valChanged();
}

//Main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include "classa.h"

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    ClassA aObj;
    QQmlApplicationEngine engine;
    engine.rootContext()->setContextProperty("classAObj",&aObj);
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    if (engine.rootObjects().isEmpty())
        return -1;

    return app.exec();
}

//Main.qml

import QtQuick 2.6
import QtQuick.Window 2.2

Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    Component.onCompleted: {
        console.log("value========",classAObj.objList[0].val)
    }
}

If i try to access "classAObj.objList[0].val" i am getting TypeError: Cannot read property 'val' of undefined error. What is that i am doing wrong here ?

SGaist

Hi,

You didn't registrer ClassB to be used by QML.

pra7

@SGaist Which one I should use Q_DECLARE_METATYPE or registermetatype ? And ClassB is already a QObject so I thought it's not required .

SGaist

ClassB, you are using it in a property.

By the way, why not use QObjectList and a Q_INVOKABLE method ? Might be more straightforward.

More information on how to integrate CPP with QML here.