QSA-interest Archive, November 2006
Problems with return values of custom type
Message 1 in thread
Hi there,
I have a problem that seems to be rather basic, but I couldn't find
info about it on the net.
I have two classes that derive from QObject:
class DbQuery: public QObject {
Q_OBJECT
public slots:
/* quite many slots, wrapping QSqlRecord */
};
class DbConnection: public QObject {
Q_OBJECT
public slots:
bool connect();
void disconnect();
DbQuery exec(QString sql);
};
I create a DbConnection object in my program and add it to my
scripting-project with addObject.
This works fine and I can connect to the database. I can call
Application.dbconnection.exec("select * from bla"); too.
But when I try to do this:
var query = Application.dbconnection.exec("select * from bla");
while( query.next() ) {
// ...
}
query is undefined.
Any thought on this issue?
By the way, QSA is by far the easiest, most integrated and seamless
scripting-framework for C++ that I've seen so far. Really, great work!
Thanks,
Daniel Albuschat
--
[ signature omitted ]
Message 2 in thread
Daniel Albuschat wrote:
> Hi there,
>
> I have a problem that seems to be rather basic, but I couldn't find
> info about it on the net.
> I have two classes that derive from QObject:
>
> class DbQuery: public QObject {
> Q_OBJECT
> public slots:
> /* quite many slots, wrapping QSqlRecord */
> };
>
> class DbConnection: public QObject {
> Q_OBJECT
> public slots:
> bool connect();
> void disconnect();
> DbQuery exec(QString sql);
> };
You cannot return DbQuery as an object on the stack as QSA doesn't know
how to generically treat these types. You have to return it as a pointer.
Btw... QObject has a private copy constructor because it cannot be
copied so if you try the code above from C++ it shouldn't even compile ;-)
best regards,
Gunnar
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Message 3 in thread
>
> You cannot return DbQuery as an object on the stack as QSA doesn't know
> how to generically treat these types. You have to return it as a pointer.
>
> Btw... QObject has a private copy constructor because it cannot be
> copied so if you try the code above from C++ it shouldn't even compile ;-)
>
The way you say that it sounds like a great achievement that QSA accepts
that code ;-) Wouldn't it be cool if QSA throws some kind of error along
the way?
/eno
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Message 4 in thread
Err, wrong reply-to header.
Here's the e-mail I've sent to Gunnar only, accidently.
---------- Forwarded message ----------
From: Daniel Albuschat <d.albuschat@xxxxxxxxx>
Date: 21.11.2006 19:49
Subject: Re: Problems with return values of custom type
To: Gunnar Sletta <gunnar@xxxxxxxxxxxxx>
2006/11/21, Gunnar Sletta <gunnar@xxxxxxxxxxxxx>:
> Daniel Albuschat wrote:
> > Hi there,
> >
> > I have a problem that seems to be rather basic, but I couldn't find
> > info about it on the net.
> > I have two classes that derive from QObject:
> >
> > class DbQuery: public QObject {
> > Q_OBJECT
> > public slots:
> > /* quite many slots, wrapping QSqlRecord */
> > };
> >
> > class DbConnection: public QObject {
> > Q_OBJECT
> > public slots:
> > bool connect();
> > void disconnect();
> > DbQuery exec(QString sql);
> > };
>
> You cannot return DbQuery as an object on the stack as QSA doesn't know
> how to generically treat these types. You have to return it as a pointer.
>
> Btw... QObject has a private copy constructor because it cannot be
> copied so if you try the code above from C++ it shouldn't even compile ;-)
I even tried it with pointers no, but it's not working that way either. I get "
TypeError. 'next' undefined or not a function"
with the following script code:
function Hello()
{
var db = Application.db_connection;
if( !db.connect("sysdba","5735","localhost","C:\\Data\\Data1.fdb","iso8859_1")
)
debug(db.lastError());
else {
var qry = db.exec("select * from prot_maingroups");
while( qry.next() ) {
}
}
}
Here's some C++ code as well. Enjoy:
class DbQuery: public QObject {
Q_OBJECT
private:
QSqlQuery q;
public:
DbQuery() { }
DbQuery(QSqlQuery q): q(q) { }
public slots:
int at () const { return q.at(); }
void clear () { return q.clear(); }
const QSqlDriver * driver () const { return q.driver(); }
bool exec ( const QString & query ) { return q.exec(query); }
bool exec () { return q.exec(); }
QString executedQuery () const { return q.executedQuery(); }
bool first () { return q.first(); }
bool isActive () const { return q.isActive(); }
bool isForwardOnly () const { return q.isForwardOnly(); }
bool isNull ( int field ) const { return q.isNull(field); }
bool isSelect () const { return q.isSelect(); }
bool isValid () const { return q.isValid(); }
bool last () { return q.last(); }
QSqlError lastError () const { return q.lastError(); }
QVariant lastInsertId () const { return q.lastInsertId(); }
QString lastQuery () const { return q.lastQuery(); }
bool next () { return q.next(); }
int numRowsAffected () const { return q.numRowsAffected(); }
bool prepare ( const QString & query ) { return q.prepare(query); }
bool previous () { return q.previous(); }
QSqlRecord record () const { return q.record(); }
const QSqlResult * result () const { return q.result(); }
bool seek ( int index, bool relative = false ) { return
q.seek(index,relative); }
void setForwardOnly ( bool forward ) { return q.setForwardOnly(forward); }
int size () const { return q.size(); }
QVariant value ( int index ) const { return q.value(index); }
};
class DbConnection: public QObject {
Q_OBJECT
private:
QSqlDatabase db;
public:
QSProject *pro;
DbConnection();
public slots:
bool connect(QString user, QString pass, QString host, QString
file, QString charset);
bool connected() const;
void disconnect();
QString lastError();
DbQuery *exec(QString sql);
};
--
[ signature omitted ]
Message 5 in thread
Daniel Albuschat wrote:
>
> I even tried it with pointers no, but it's not working that way
> either. I get " TypeError. 'next' undefined or not a function" with
> the following script code:
Sorry, forgot to mention that custom QObject types have to registered using:
http://doc.trolltech.com/qsa-1.2.1/qsinterpreter.html#registerMetaObject
I hope this makes it work.
best regards,
Gunnar
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