Populate ComboBox from QList<QObject*> - qt

Question

I was following an example on web to populate combobox, but it did not wok for me and I do not know why!. I have two classes stock and DbCon, stock has three private fields along with public accessor and mutators. DbCon has a Q_Property and two public function, one returns a database connection and the other creates and returns stock list as a QList<QObject*>. In main.cpp I have created a contextual property named "data" to access DbCon from QML.
in main.qml I have
....
ComboBox{
model: data.stockModel
textRole: "code"
}
....
in main.cpp
DbCon db;
engine.rootContext()->setContextProperty("data", &db);
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
in dbcon.h
class DbCon:public QObject
{
Q_OBJECT
Q_PROPERTY(QList<QObject*> stockModel READ stockModel)
public:
explicit DbCon(QObject *parent = 0);
QSqlDatabase db();
QList<QObject*> stockModel();
};
in implementation of QList<QObject*> stockModel() of dbcon.h
QList<QObject*> data;
....
while (query.next()) {
stock *s = new stock();
....
data.append(s);
}
return data;
and in stock.h
class stock : public QObject
{
Q_OBJECT
private:
QString m_name;
QString m_code;
int m_id;
public:
explicit stock(QObject *parent = 0);
QString name();
void setname(QString &name);
QString code();
void setcode(QString &code);
int id();
void setid(int &id);
};
When I run the application I get the following message in application output
QQmlExpression: Expression qrc:/main.qml:16:20 depends on non-NOTIFYable properties:
QQuickComboBox::data
and I do not get anything in combobox!
If I create another contextual property in main.cpp in this way
engine.rootContext()->setContextProperty("myModel", QVariant::fromValue(data));
and set myModel as model for combobox, it works fine. But I want to do it in this way because onCurrentIndexChanged I will call another function that returns another QList<QObject*> for a TableView of another qml file.
EDIT: Entrie qml
import QtQuick 2.5
import QtQuick.Window 2.2
import QtQuick.Controls 2.0
Window {
visible: true
width:600
height:600
property string contentSource
Column{
spacing:10
ComboBox{
model: data.stockModel
textRole: "code"
}
Loader {
id: content
width: parent.width
height:400
}
Row{
spacing:10
Button{
text: "Page1"
onClicked: content.source = "Page1.qml"
}
Button{
text: "Page2"
onClicked: content.source = "Page2.qml"
}
}
}
}
By changing data to dataStore in main.cpp and data.stockModel to dataStore.stockModel in main.qml I get following error
file:///C:/Qt/Qt5.7.0/5.7/mingw53_32/qml/QtQuick/Controls.2/ComboBox.qml:62:15: Unable to assign [undefined] to QString

Answer 1

You have two issues:
Your stockModel property should be NOTIFYable, which means that you should define the property with e.g. Q_PROPERTY(QList<QObject*> stockModel READ stockModel NOTIFY stockModelChanged) and provide a void stockModelChanged(const QList<QObject *> &) signal in the DbCon class.
stock::name() must be a property too, so you need to declare that with Q_PROPERTY(QString name READ name NOTIFY nameChanged) and provide a void nameChanged(const QString &) signal in the stock class as well.