[Qt-interest] Design of Qt/DB applications

[Jason H]

Once you connect to a database, unless you specify the database as a parameter, it will use the connected database.

Your only problem is that that "db" goes away. If you have only one connection for your app, put it in your main() or QMainDialog-derived instance.





________________________________
From: William Lugg <wlugg at prairienetworks.com>
To: qt-interest at trolltech.com
Sent: Tue, January 26, 2010 8:37:58 PM
Subject: [Qt-interest] Design of Qt/DB applications

OK, here's what may be a duh question.

I've been trying to study the SQL examples and figure that out, but have failed.  I'm working on an application that will provide a rather elaborate membership roster for an organization.  It is using SQLite for the DB engine and Qt  (obviously) for the GUI.  I've build a simple class to handle the connection of the app to the DB and got the impression from the examples that I should place a call to the static connection::createConnection() in main.cpp before I started the app itself.  However, after some debugging, I'm discovering that it looks like I need the createConnection call in each form and dialog I open that needs access to the DB.  Is the correct or am I not doing the right things in my createConnection code?  Here's the code if that helps...

bool Connection::createConnection()
{
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE", "rlhs_db");


db.setDatabaseName("../database/rlhs_db");
if (db.open())
{
return true;
}
else
{
QMessageBox::critical(0,
qApp->tr( "Cannot open database"),
qApp->tr( "Unable to establish a database connection.\n"
"This application needs SQLite support. Please read "
"the Qt SQL driver documentation for information how "
"to build it.\n\n"
"Click Cancel to exit."),
QMessageBox::Cancel);


return false;
}
}

Looks a lot like the example code, doesn't it?  :o)

Thanks for the help.
----
Bill Lugg
Milstar Software Support
Peterson AFB, CO
No Micro$oft products were used to create this email. 
God rules and if He needed a computer it would run Linux!


      
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