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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
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<title>QOF GObject Usage Example</title>
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<h1>Query Over a Collection of GObjects</h1>
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<div><p>The example below shows how to perform an SQL query over
a collection of Glib GObjects. Three
<b><tt>GtkButton</tt></b> objects are created, each with
a different label. Then the SQL statement
<b><tt>SELECT * FROM GtkButton WHERE (label='asdfasdf');</tt></b>
is performed on this collection. The one button with the
matching label is returned.</p>
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<pre>
/** @file gobj-example.c
* @brief Example usage of QOF to query a set of GObjects.
* @author Copyright (c) 2004 Linas Vepstas <linas@linas.org>
*
* This example program shows how to use QOF to query over a set
* of GObjects. In this example, the query is performed over
* three GtkButtons, each having a different label. The result
* of the search is the one GtkButton with the desired label.
*
* The use of GtkButton in this example is artificial. GLib
* GObjects do not have to be GUI objects, and can be created
* for any use desired. I didn't want to turn this into an
* example of how to create a GObject, and so used a pre-existing
* GObject, the GtkButton.
*/
#include <qof/qof.h>
#include <gtk/gtk.h>
int
main(int argc, char *argv[])
{
g_type_init ();
gtk_init (&argc, &argv);
qof_gobject_init ();
/* Register a new searchable type */
GtkWidget *w = gtk_button_new_with_label ("Howdy Doody");
GtkButtonClass * wc = GTK_BUTTON_GET_CLASS(w);
GObjectClass *goc = G_OBJECT_CLASS(wc);
qof_gobject_register ("MyGtkButton", goc);
/* Add a number of instances to the collection */
QofBook *book = qof_book_new();
qof_gobject_register_instance (book, "MyGtkButton", G_OBJECT(w));
w = gtk_button_new_with_label ("dorf");
qof_gobject_register_instance (book, "MyGtkButton", G_OBJECT(w));
w = gtk_button_new_with_label ("zinger");
qof_gobject_register_instance (book, "MyGtkButton", G_OBJECT(w));
printf ("\nCreated three objects and registered them\n\n");
/* Create a new query, run that query */
QofSqlQuery *q;
q = qof_sql_query_new ();
/* Set the book to be searched */
qof_sql_query_set_book(q, book);
char * qstr = "SELECT * FROM MyGtkButton WHERE (label = 'dorf')";
printf ("Going to perform the query %s\n", qstr);
GList *results = qof_sql_query_run (q, qstr);
printf ("\nQuery returned %d results\n", g_list_length (results));
GList *n;
for (n=results; n; n=n->next)
{
GtkWidget *qw = n->data;
if (GTK_IS_BUTTON(qw))
{
GtkButton *bw = GTK_BUTTON (qw);
printf ("Found a button whose label is %s\n", gtk_button_get_label(bw));
}
}
qof_gobject_shutdown ();
return 0;
}
/* =================== END OF FILE ===================== */
</pre>
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