Possible to wrap non-QObject C++ object by an Entrymodel?

[Tobias83]

Oh, I'm sorry! I thought Entrymodel is a common Qt name. I do this:
class Hardcore_Entrymodel : public QAbstractListModel

[Tobias83]

@JonB Hello JonB,
OK, it's not? I thought its a bit like OpenGL - there is such a loop I think ...

[Bob64]

@Tobias83 OK, so Entrymodel is just part of the name of your class which implements a QAbstractListModel.

How is your list model used in your application? If you want to expose it to QML so that you can actually instantiate it in QML, like this

ListModel {
    model: Hardcore_EntryModel {
    }
    ...
}

then you are restricted to not being able to pass arguments into your constructor.

On the other hand if you want to be able to instantiate your model in C++ and just make that instance accessible in QML, you are potentially less restricted. In your C++ you can instantiate your Hardcore_EntryModel however you want and use qmlRegisterSingletonInstance:

Hardcore_EntryModel entryModel(arg1, arg2, ...);
qmlRegisterSingletonInstance("mytypes", 1, 0, "EntryModel", &entryModel);

and then use it in your QML:

ListModel {
    model: EntryModel // use the singleton instance exposed in the C++
    ...
}

[Tobias83]

@Bob64 Thanks! I will try this tomorrow ...

[Tobias83]

@Bob64 Dear Bob64,
How do I have to handle this contructor:

explicit Hardcore_Entrymodel(QObject *parent=0, System* system);

Is the =0 correct?
If I call it like this, it errors:

tw_hardcoresystem::Hardcore_EntryModel entryModel(nullptr, &system);

It also errors with this constructor, because there is a QAbstractListModel(parent) which needs the parent argument:

explicit Hardcore_Entrymodel(System* system);

Thank you for your Help!

Tobias

[JonB]

@Tobias83 said in Possible to wrap non-QObject C++ object by an Entrymodel?:

explicit Hardcore_Entrymodel(QObject *parent=0, System* system);

Per C++, any optional/default-value parameters can only come after any mandatory ones. Your code is not legal because a parameter without a default comes after one with a default. Either give a default for System* system as well, or (preferable IMO) make the system parameter come before the parent one. I would always leave a QObject-derived constructor taking QObject *parent = nullptr as the last argument.

[Tobias83]

@Tobias83 I now found an a little bit different solution. In stackoverflow someone suggested set and get functions. So I have:

public:
    explicit Hardcore_Entrymodel();
    //explicit Hardcore_Entrymodel(QObject *parent, System* system);
    void setSystem(System* system);

and in the main fct:

    Hardcore_Entrymodel entryModel;
    entryModel.setSystem(&system);
    qmlRegisterSingletonInstance("hardcoresystem", 1, 0, "Hardcoreentrymodel", &entryModel);

For this, it draws a window and the "QML Object is not creatable" error disappears.

But there are still some little mistake, which are not related to Qt, I think.

Thanks a lot until here!!!

kind regards,
Tobias

PS: if the std::stof function in one case outputs the double value of a string, and some loops later gives the integer value - it is not related to Qt? What can this be? A corrupt compiler?

[JonB]

@Tobias83
std::stof() has nothing to do with Qt, you do not have a "corrupt compiler" and even if you did that would not change its behaviour according to how many times it is called. It returns a float. It does not return an int, though of course a value returned might happen to be an integer (as in, no decimal places).

[Tobias83]

This post is deleted!

[Tobias83]

Does the QAbstractListModel work the same as Singleton if data is changed. In QML I have a Repeater which draws the particles. But if I do a simulation step, the picture in in the window is not updated, but the coordinates in cpp are. On the console I get the output qml: DataChanged received.

This my step method:

void Hardcore_Entrymodel::doNewStep()
{
    emit newStepDoing();
    hardcoresystem->testStep();
    populate();

    return;
}

and populate looks like that:

void Hardcore_Entrymodel::populate()
{
    int ipart;
    for(ipart=0; ipart<nparticles; ipart++){
        mDatas[ipart]= initqtview.SystemToWindow(hardcoresystem->returnIParticle(ipart));
    }
    emit dataChanged(index(0),index(nparticles));
    return;
}

And the step is made by mouseclick in qml:

MouseArea {
            anchors.fill: parent
            onClicked: Hardcoreentrymodel.doNewStep()
        }