[Solved] best way to delegate through sqlite data for qml list view

SGaist

Hi,

"This":http://stackoverflow.com/questions/16658360/integrating-sqlite-with-qt-quick might help you

gloww

Hi SGaist,

thanks for the link. I thought that there is maybe an easier way to do this only with qml but to do it with c++ gives much more possibilities.

I tried the example in the link but got an error.
I am having the problem that RoleNameHash seems not to be defined/included.
@
'RoleNameHash' does not name a type@

@#ifndef SQLQUERYMODEL_H
#define SQLQUERYMODEL_H

#include <QtSql>

class SqlQueryModel: public QSqlQueryModel
{
Q_OBJECT
QHash<int,QByteArray> *hash;
public:
explicit SqlQueryModel(QObject * parent) : QSqlQueryModel(parent)
{
hash = new QHash<int,QByteArray>;
hash->insert(Qt::UserRole, QByteArray("someRoleName"));
hash->insert(Qt::UserRole + 1, QByteArray("otherRoleName"));
}
QVariant data(const QModelIndex &index, int role) const
{
if(role < Qt::UserRole) {
return QSqlQueryModel::data(index, role);
}
QSqlRecord r = record(index.row());
return r.value(QString(hash->value(role))).toString();
}
inline RoleNameHash roleNames() const { return *hash; }
};

#endif // SQLQUERYMODEL_H @

gloww

Ich changed the line to:
@inline QHash<int,QByteArray> roleNames() const { return *hash; }@

now i get:
@QSqlQuery::exec: database not open@

I think I should read me deeper into the whole QT SQL topic.

gloww

Hey,

i solved it. It is really simple. I am wondering why there is not such an simple example anywhere.

main.cpp
@
#include <QApplication>
#include <QQmlApplicationEngine>
#include <QQmlComponent>
#include <QQmlContext>
#include <QtSql/QSqlDatabase>
#include <QtSql/QSqlQueryModel>
#include <QtSql/QSqlQuery>
#include <QDebug>

int main(int argc, char *argv[])
{
QApplication app(argc, argv);

QQmlApplicationEngine engine;

QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName("my.db.sqlite");
if(!db.open()){
    qDebug("not open!");
}else{
    qDebug("db open!");

}

//QSqlQuery drop("drop table List;");
//QSqlQuery create("create table List (sample_text char(200));");
QSqlQuery insert("insert into List values (\"some blaaahahhh!\");");

//drop.exec&#40;&#41;;
//create.exec&#40;&#41;;
insert.exec&#40;&#41;;


QSqlQueryModel *someSqlModel = new QSqlQueryModel();
someSqlModel->setQuery("SELECT * FROM List");

//db.close();
engine.rootContext()->setContextProperty("datamodel", someSqlModel);

engine.load(QUrl(QStringLiteral("qrc:///main.qml")));

return app.exec();

}@

in the qml:

@ Rectangle {
ListView {
width: 200; height: 200
model: datamodel
delegate: Row {
Rectangle {
width: 100; height: 40
Text {
anchors.fill: parent
text: display
}
}
}
}
}@

gloww

Ah, one thing i dont understand is how i can get different rows of the result in my qml delegate. at the moment there is:
@
text: display@

this has nothing to do with my data. is this something like a wildcard?
in my opninion it should look like the following but this is not working:

@
text: sample_text @

SGaist

If you want to display different things, you have to provide you own roles and use them to access your model

gloww

I realized it just some seconds ago. thanks anyways.

here is my current implementation:

@#ifndef SQLQUERYMODEL_H
#define SQLQUERYMODEL_H

#include <QtSql>
#include <QAbstractItemModel>

class SqlQueryModel: public QSqlQueryModel
{
Q_OBJECT
QHash<int,QByteArray> *hash;
public:
explicit SqlQueryModel() : QSqlQueryModel()
{
hash = new QHash<int,QByteArray>;
hash->insert(Qt::UserRole, QByteArray("name"));
hash->insert(Qt::UserRole + 1, QByteArray("title"));
}
QVariant data(const QModelIndex &index, int role) const
{
if(role < Qt::UserRole) {
return QSqlQueryModel::data(index, role);
}
QSqlRecord r = record(index.row());
return r.value(QString(hash->value(role))).toString();
}
inline QHash<int, QByteArray> roleNames() const { return *hash; }
};

#endif // SQLQUERYMODEL_H
@

SGaist

One thing you should change: don't use pointers to QHash, there's no need for that. Qt uses implicit sharing for it's containers class as well as heap allocation so you would only rarely need to allocate a QHash on the heap. Also, you don't delete it in any destructor so you are creating a memory leak.

gloww

Thanks for the hint. I changed this already. Should I add a destructor or do you think it is enough when i store it only on the stack instead of the heap...

SGaist

It's up to you, you can also use a QScopedPointer so you don't have to delete someSqlModel yourself