How to register a class inherited from QQmlPropertyValueSource?

Anton1978

Good afternoon.
Version Qt6 6.5. I want to make the class visible in QML, it worked, but QML does not see the class field.
The class itself

#ifndef RANDOMNUMBER_H
#define RANDOMNUMBER_H
 
#include <QObject>
#include <QQmlProperty>
#include <QQmlPropertyValueSource>
#include <qqml.h>
 
class QTimer;
 
class RandomNumber : public QObject, public QQmlPropertyValueSource
{
    Q_OBJECT
    Q_PROPERTY(int maxValue READ maxValue WRITE setMaxValue NOTIFY maxValueChanged FINAL)
    Q_INTERFACES(QQmlPropertyValueSource)
    // QML_ELEMENT
    // QML_VALUE_TYPE(RandomNumber)
 
public:
    explicit RandomNumber(QObject *parent = nullptr);
    virtual void settarget(const QQmlProperty &pop);
    int maxValue() const;
    void setMaxValue(int newMaxValue);
 
signals:
    void maxValueChanged();
 
public slots:
    void updatePropety();
 
private:
    QQmlProperty _targetPropety;
    QTimer *_timer = nullptr;
    int m_maxValue;
};
 
#endif // RANDOMNUMBER_H

realization

#include "randomnumber.h"
#include <qtimer.h>
#include <QObject>
#include <QRandomGenerator64>
 
RandomNumber::RandomNumber(QObject *parent)
{
    m_maxValue = 100;
    _timer = new QTimer();
    QObject::connect(_timer,&QTimer::timeout,this,&RandomNumber::updatePropety);
    _timer->start(1000);
}
 
void RandomNumber::settarget(const QQmlProperty &pop)
{
    _targetPropety = pop;
}
 
int RandomNumber::maxValue() const
{
    return m_maxValue;
}
 
void RandomNumber::updatePropety()
{
    _targetPropety.write(QRandomGenerator64::global()->bounded(m_maxValue));
}
 
void RandomNumber::setMaxValue(int newMaxValue)
{
    if (m_maxValue == newMaxValue) return;
    m_maxValue = newMaxValue;
    emit maxValueChanged();
}

and part of QML

import RandomNumber 1.0
 
//еще код
 
    Rectangle{
        id: rectus
        color: "red"
        width: 150
        height: 150
        RandomNumber  on radius  //here is our class
        {
            maxValue : 50 // and our propetis
        }
        Text{
            //text: moo.HuiNia();
            text: wooda.word + func();
        }
    }

class is not registered, I tried like this

qmlRegisterType<RandomNumber>("RandomNumber",1,1,"RandomNumber"); //didn't work - reports that abstract type cannot be registered
 
qmlRegisterType<RandomNumber>("RandomNumber",1,1,"RandomNumber","Cant create"); //
it registers like this, but as expected it doesn’t work in QML
 
qmlRegisterExtendedType<RandomNumber>("RandomNumber",1,1,"RandomNumber"); // does not register, the error message is not clear to me

What does he want??? How to register a C++ class so that you can already use it?

GrecKo

qmlRegisterType<RandomNumber>("RandomNumber",1,1,"RandomNumber"); //didn't work - reports that abstract type cannot be registered

Make your class not abstract: override the pure virtual function virtual void setTarget(const QQmlProperty &property) = 0.

You declared virtual void settarget(const QQmlProperty &pop); which is a typo.
When overriding a function don't specify virtual (it's useless) but add override at the end to make sure you are actually overriding something.
The following would have gave you a compile error since it was marked as override but didn't override anything:

void settarget(const QQmlProperty &pop) override;

Also prefer QML_ELEMENT macros over qmlRegisterType.

Anton1978

It doesn't work.

void settarget(const QQmlProperty &pop) override;

this doesn't work in principle, there's nothing to overload there. Why did I write so strangely? Because I’ve only been studying this for three days and was guided by one video, here
I think virtual is not really needed, but who knows. But there is version 5.11.
I also tried to do this

class RandomNumber : public QObject, public QQmlPropertyValueSource
{
    Q_OBJECT
    Q_PROPERTY(int maxValue READ maxValue WRITE setMaxValue NOTIFY maxValueChanged FINAL)
    Q_INTERFACES(QQmlPropertyValueSource)
    QML_ELEMENT

and in the file, CMakeLists.txt

qt6_add_qml_module(RandomNumber
  URI randomNumber
  VERSION 1.0
)

But this doesn’t work either, it compiles, but class is not visible in QML (if you use it, there will be an error).
I really don’t understand what is needed, everything worked in the video tutorial.
Just in case, here is my entire project

jsulm

@Anton1978 said in How to register a class inherited from QQmlPropertyValueSource?:

this doesn't work in principle

Of course not, because it is setTarget, not settarget as was pointed out by @GrecKo

Anton1978

and nothing
build error - :-1: ninja: build stopped: subcommand failed.
wait, I didn't clean CMakeLists.txt

Anton1978

yes, now it works.
Thank you very much

jsulm

@Anton1978 said in How to register a class inherited from QQmlPropertyValueSource?:

build error - :-1: ninja: build stopped: subcommand failed.

Just a tipp: what you posted is not the actual error, in such cases you should look above that to find the real error message.