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/** @file my-object.c
* @breif Example definition of a queriable object.
* @author Copyright (c) 2003,2004 Linas Vepstas <linas@linas.org>
*
* This example program shows how to configure an arbitrary
* programmer-defined object "MyObj" so that the Query routines
* can be used on it. It shows one part of the total:
* -- The object definition, showing how to hook into the query system.
*
* Please make note of how the 'book' is used. A 'book' can serve
* as a collection of collections. In the example below, the book
* will be used to hold all of the instances of 'my object' so that
* these can be found later. Note that the book doesn't need to
* exclusively hold only instances of 'my object', it can hold
* collections of other types as well.
*
* The above ability is one reason why 'book' holds such a central
* place in the QOF system. Note also: when the query is performed
* over all instances of 'my object', its not really over *all*
* instances; its only over those instances stored in the given book.
* Thus, the book is a kind of dataset, and by using books, one
* can have multiple disjoint datasets.
*/
#include <glib.h>
#include <qof/qof.h>
#include "my-object.h"
/* ===================================================== */
MyObj *
my_obj_new (QofBook *book)
{
MyObj *m = g_new0 (MyObj,1);
/* Make sure we keep track of every object;
* otherwise we won't be able to search over them.
* Do this by storing them in a collection.
*
* Although we use a 'collection' in this example, there is no
* requirement that this be done. One could use a global variable
* or something else. The only requirement is that the 'foreach'
* below is able to find every object.
*
* The collection 'data' pointer can be used to store any kind
* of user-defined data. Here, we use it to hold a linked
* list (the GList), but it could have held anything. Most
* other objects (e.g. GnuCash objects) probably don't use the
* data pointer in this way.
*/
QofCollection *coll = qof_book_get_collection (book, MYOBJ_ID);
GList *all_my_objs = qof_collection_get_data (coll);
all_my_objs = g_list_prepend (all_my_objs, m);
qof_collection_set_data (coll, all_my_objs);
return m;
}
/* Generic object getters */
int
my_obj_get_a (MyObj *m)
{
return m->a;
}
int
my_obj_get_b (MyObj *m)
{
return m->b;
}
const char *
my_obj_get_memo (MyObj *m)
{
return m->memo;
}
/* Loop over every instance of MyObj, and apply the callback to it.
* This routine must be defined for queries to be possible.
*/
void
my_obj_foreach (QofCollection *coll, QofEntityForeachCB cb, gpointer ud)
{
GList *n;
GList *all_my_objs = qof_collection_get_data (coll);
for (n=all_my_objs; n; n=n->next)
{
cb (n->data, ud);
}
}
/* Provide a default mechanism to sort MyObj.
* This is neeeded so that query results can be returned in
* some 'reasonable' order. If you don't want to sort,
* just have this function always return 0.
*/
int
my_obj_order (MyObj *a, MyObj *b)
{
if ( (a) && !(b) ) return -1;
if ( !(a) && (b) ) return +1;
if ( !(a) && !(b) ) return 0;
if ((a)->a > (b)->a) return +1;
if ((a)->a == (b)->a) return 0;
return -1;
}
/* ===================================================== */
/* Provide infrastructure to register my object with QOF */
static QofObject myobj_object_def =
{
interface_version: QOF_OBJECT_VERSION,
e_type: MYOBJ_ID,
type_label: "My Blinking Object",
new: my_obj_new,
book_begin: NULL,
book_end: NULL,
is_dirty: NULL,
mark_clean: NULL,
foreach: my_obj_foreach,
printable: NULL,
};
gboolean myObjRegister (void)
{
/* Associate an ASCII name to each getter, as well as the return type */
static QofParam params[] = {
{ MYOBJ_A, QOF_TYPE_INT32, (QofAccessFunc)my_obj_get_a, NULL },
{ MYOBJ_B, QOF_TYPE_INT32, (QofAccessFunc)my_obj_get_b, NULL },
{ MYOBJ_MEMO, QOF_TYPE_STRING, (QofAccessFunc)my_obj_get_memo, NULL },
{ NULL },
};
qof_class_register (MYOBJ_ID, (QofSortFunc)my_obj_order, params);
return qof_object_register (&myobj_object_def);
}
/* =================== END OF FILE ===================== */
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