Grouped Property Problem

maydin

I am following this example: http://doc.qt.io/qt-5/qtqml-cppintegration-exposecppattributes.html#grouped-properties

When I want to access them I get this error: Invalid grouped property access

Bataque {
        id: bataque
        model.name: "asd"
        author.name: "abc"
}

I am doing something wrong in registering types. I tried almost everything but could not find the solution.

And my code is like this:


    qmlRegisterType<Batak>("backend", 1, 0, "Bataque");
//    qmlRegisterType< Model >();          //>> These does not work also. Different errors.
//    qRegisterMetaType<Model*>("Model*");
    qmlRegisterUncreatableType<Model>("backend", 1, 0, "Modelito", "something wrong");

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

class Bataque: public QObject
{
    Q_OBJECT
    Q_PROPERTY(Model* model READ model)
    Q_PROPERTY(Model* author READ author)
    Model m_model;
    Model* m_author;

public:
    explicit Bataque(QObject *parent = nullptr): QObject(parent), m_author(new Model(this))
    {
    }
    Model* model()
    {
        return &m_model;
    }
    Model* author() const
    {
        return m_author;
    }
};

#include <QObject>
#include <QString>

class Model : public QObject
{
    Q_PROPERTY(QString name READ name WRITE setName)

public:
explicit Model(QObject *parent = nullptr) : QObject(parent) {}

QString name() const
{
    return m_name;
}

public slots:
void setName(QString name)
{
    m_name = name;
}
private:
QString m_name;
};

KillerSmath

@maydin
Hi there, welcome to Qt Forum.

I've checked your code and noticed some "mistakes" or confusion on coding.

1) You forgot of Q_OBJECT macro on Model.h file.

class Model : public QObject
{
    Q_OBJECT
    Q_PROPERTY(QString name READ name WRITE setName)
...

2) You don't necessarily need to define in public slot scope to call the read function of Q_PROPERTY, although this works the same way.

// Model.h //

public: // public scope
explicit Model(QObject *parent = nullptr) : QObject(parent) {}

QString name() const
{
    return m_name;
}

//public slots:
void setName(QString name) // defined as public
{
    m_name = name;
}
private:
QString m_name;
};

3) You explicitly need to say: "I have an object that can be converted from QVariant to Model"

 // main function
 qmlRegisterType<Model>(); // this line is necessary
 qmlRegisterType<Bataque>("backend", 1, 0, "Bataque");

Bonus:

Qt Creator has a shortcut key to Auto Identation of your code - Ctrl + I

maydin

@KillerSmath

I did not forgot Q_OBJECT. In example of Qt Docs there is no Q_OBJECT macro. I tried adding that also but it gave me moc errors.
I just used Alt+Space and clicked "Generate missing property members". Those was done automatically.
Added qmlRegisterType<Model>(); but still same error.

KillerSmath

Okay, we are progressing.

@maydin said in Grouped Property Problem:

I did not forgot Q_OBJECT. In example of Qt Docs there is no Q_OBJECT macro. I tried adding that also but it gave me moc errors.

Yes, i noticed that in this example has not Q_OBJECT, but this macro allow some features of Meta-Object.

Q_OBJECT

The Q_OBJECT macro must appear in the private section of a class definition that declares its own signals and slots or that uses other services provided by Qt's meta-object system.

Q_PROPERTY

This macro is used for declaring properties in classes that inherit QObject. Properties behave like class data members, but they have additional features accessible through the Meta-Object System.

When i remove the Q_OBJECT macro, i got the below message from Qt Log window:

References:
http://doc.qt.io/qt-5/qobject.html#Q_OBJECT
http://doc.qt.io/qt-5/qobject.html#Q_PROPERTY

maydin

@KillerSmath

Okay, I added Q_OBJECT macro on Model class. And registering codes is like this:

    qmlRegisterType<Bataque>("backend", 1, 0, "Bataque");
    qmlRegisterType< Model >();
//    qRegisterMetaType<Model*>("Model*");
    qmlRegisterUncreatableType<Model>("backend", 1, 0, "Modelito", "something wrong");

Here the errors i see:

alt text

As i said before, if i dont add Q_OBJECT macro i can compile without errors and QML engine see my objects without error. Problem occurs at runtime. If I add that macro i cannot even compile.

GrecKo

Those are errors caused by the MOC not being called.
Clean and rebuild your project or run qmake manually.

maydin

Finally I solved.

These MOC errors came from qmake not updating when you add a Qt macro somewhere.
If you are using split screen and make changes at right side of screen, sometimes qmake doesnt update. I often run qmake manually for QML files but didn't know this should be done for C++ files too.

I used both pointer and normal versions of Model instances in Bataque class. Both of them work in QML. You can register them by using one of following functions.

// Both of them working individually
qmlRegisterType< Model >();
qmlRegisterUncreatableType<Model>("backend", 1, 0, "Modelito", "something wrong");