How to expose a C++ Model to QML

Question

I'm writing a QML+Qt application . I defined a class like this :

class MainClass : public QObject
{
    Q_OBJECT

public:
    rosterItemModel m_rosterItemModel;
.
.
.
}

rosterItemModel model is a class derived from QAbstractListModel. I exposed MainClass to qml part using this function :

qmlRegisterType<MainClass>("CPPIntegrate", 1, 0, "MainClass");

Now I want to assign this model(m_rosterItemModel) from MainClass to model property of a ListView in QML. I tried the following ways but none of them were helpful :(

• I tried to declare m_rosterItemModel as a PROPERTY using Q_PROPERTY . I couldn't do that because it said that QAbstractListModel is not copy-able.
• I tried to get a pointer to m_rosterItemModel in qml file using a Q_INVOKABLE function in MainClass. But it wasn't helpful too.

Could someone help me?

Answer 1

There shouldn't be any metatype registration necessary. All you need to is to call setContextProperty and pass the model by pointer:

QQmlContext* context = view->rootContext(); //view is the QDeclarativeView
context->setContextProperty( "_rosterItemModel", &mainClassInstance->m_rosterItemModel );

Use it in QML:

model: _rosterItemModel

By pointer is important, as QObject's are not copy-constructible and copying them would break their semantics anyway (as they have an "identity").

The alternative to registering the model directly is to register your main class' instance and using Q_INVOKABLE. In MainClass:

Q_INVOKABLE RosterItemModel* rosterItemModel() const;

Registering an instance of mainClass (mainClassInstance again is assumed to be a pointer):

context->setContextProperty( "_mainInstance", mainClassInstance );

In QML:

model: _mainInstance.rosterItemModel()