Object: Describing data structure.
[Query Object Framework]

Data Structures
struct	_QofObject
Modules
	Object_Private
	GLib GObjects
Files
file	qofobject.h
	the Core Object Description Interface
Defines
#define	QOF_OBJECT_VERSION   3
#define	QOF_MOD_OBJECT   "qof-object"
Typedefs
typedef struct _QofObject	QofObject
typedef void(*	QofForeachCB )(gpointer obj, gpointer user_data)
typedef void(*	QofForeachTypeCB )(QofObject *type, gpointer user_data)
typedef void(*	QofForeachBackendTypeCB )(QofIdTypeConst type, gpointer backend_data, gpointer user_data)
Functions
gboolean	qof_object_register (const QofObject *object)
const QofObject *	qof_object_lookup (QofIdTypeConst type_name)
gpointer	qof_object_new_instance (QofIdTypeConst type_name, QofBook *book)
const gchar *	qof_object_get_type_label (QofIdTypeConst type_name)
const gchar *	qof_object_printable (QofIdTypeConst type_name, gpointer instance)
void	qof_object_foreach_type (QofForeachTypeCB cb, gpointer user_data)
void	qof_object_foreach (QofIdTypeConst type_name, QofBook *book, QofEntityForeachCB cb, gpointer user_data)
gboolean	qof_object_register_backend (QofIdTypeConst type_name, const gchar *backend_name, gpointer be_data)
gpointer	qof_object_lookup_backend (QofIdTypeConst type_name, const gchar *backend_name)
void	qof_object_foreach_backend (const char *backend_name, QofForeachBackendTypeCB cb, gpointer user_data)
Initialize the object registration subsystem
void	qof_object_initialize (void)
void	qof_object_shutdown (void)

---

Detailed Description

QOF Objects provide the means for describing a QofEntity to allow a storage backend to load and write a QofBook. While an entity can be thought of as an identified instance of some thing, the QOF Object describes how that entity can be created, how to find other entities of the same type, whether the object can be cached in the backend and how to compare entities of the same type.

• QofObject describes how to relate one entity to another.
• QofClass describes how to get and set data within the entity.

To work with your own QOF Objects, you can use the QOF Generator to create sample objects and a mini-application with the SQL-type query interface. http://qof-gen.sourceforge.net/

---

Define Documentation

#define QOF_OBJECT_VERSION   3

Defines the version of the core object object registration interface. Only object modules compiled against this version of the interface will load properly

Definition at line 57 of file qofobject.h.

---

Function Documentation

void qof_object_foreach	(	QofIdTypeConst	type_name,
		QofBook *	book,
		QofEntityForeachCB	cb,
		gpointer	user_data
	)

Invoke the callback 'cb' on every instance ov a particular object type. It is presumed that the 'book' stores or somehow identifies a colllection of instances; thus the callback will be invoked only for those instances stored in the book.

Definition at line 174 of file qofobject.c.

{
    QofCollection *col;
    const QofObject *obj;

    if (!book || !type_name)
    {
        return;
    }
    PINFO ("type=%s", type_name);

    obj = qof_object_lookup (type_name);
    if (!obj)
    {
        PERR ("No object of type %s", type_name);
        return;
    }
    col = qof_book_get_collection (book, obj->e_type);
    if (!obj)
    {
        return;
    }
    if (obj->foreach)
    {
        obj->foreach (col, cb, user_data);
    }
    return;
}

void qof_object_foreach_type	(	QofForeachTypeCB	cb,
		gpointer	user_data
	)

Invoke the callback 'cb' on every object class definition. The user_data pointer is passed back to the callback.

Definition at line 140 of file qofobject.c.

{
    GList *l;

    if (!cb)
        return;

    for (l = object_modules; l; l = l->next)
    {
        QofObject *obj = l->data;
        (cb) (obj, user_data);
    }
}

const gchar* qof_object_get_type_label

(

QofIdTypeConst

type_name

)

Get the printable label for a type. This label is *not* translated; you must use _() on it if you want a translated version.

Definition at line 223 of file qofobject.c.

{
    const QofObject *obj;

    if (!type_name)
        return NULL;

    obj = qof_object_lookup (type_name);
    if (!obj)
        return NULL;

    return (obj->type_label);
}

void qof_object_initialize

(

void

)

Definition at line 248 of file qofobject.c.

{
    if (object_is_initialized)
        return;
    backend_data = g_hash_table_new (g_str_hash, g_str_equal);
    object_is_initialized = TRUE;
}

const QofObject* qof_object_lookup

(

QofIdTypeConst

type_name

)

Lookup an object definition

Definition at line 305 of file qofobject.c.

{
    GList *qiter;
    const QofObject *obj;

    g_return_val_if_fail (object_is_initialized, NULL);

    if (!name)
        return NULL;

    for (qiter = object_modules; qiter; qiter = qiter->next)
    {
        obj = qiter->data;
        if (!safe_strcmp (obj->e_type, name))
            return obj;
    }
    return NULL;
}

gpointer qof_object_new_instance	(	QofIdTypeConst	type_name,
		QofBook *	book
	)

Create an instance of the indicated type, returning a pointer to that instance. This routine just calls the (*new) callback on the object definition.

Definition at line 42 of file qofobject.c.

{
    const QofObject *obj;

    if (!type_name)
        return NULL;

    obj = qof_object_lookup (type_name);
    if (!obj)
        return NULL;

    if (obj->create)
        return (obj->create (book));

    return NULL;
}

const gchar* qof_object_printable	(	QofIdTypeConst	type_name,
		gpointer	instance
	)

Returns:

a Human-readable string name for an instance

Definition at line 205 of file qofobject.c.

{
    const QofObject *b_obj;

    if (!type_name || !obj)
        return NULL;

    b_obj = qof_object_lookup (type_name);
    if (!b_obj)
        return NULL;

    if (b_obj->printable)
        return (b_obj->printable (obj));

    return NULL;
}

gboolean qof_object_register

(

const QofObject *

object

)

Register new types of object objects

Definition at line 278 of file qofobject.c.

{
    g_return_val_if_fail (object_is_initialized, FALSE);

    if (!object)
        return FALSE;
    g_return_val_if_fail (object->interface_version == QOF_OBJECT_VERSION,
        FALSE);

    if (g_list_index (object_modules, (gpointer) object) == -1)
        object_modules =
            g_list_prepend (object_modules, (gpointer) object);
    else
        return FALSE;

    /* Now initialize all the known books */
    if (object->book_begin && book_list)
    {
        GList *node;
        for (node = book_list; node; node = node->next)
            object->book_begin (node->data);
    }

    return TRUE;
}

gboolean qof_object_register_backend	(	QofIdTypeConst	type_name,
		const gchar *	backend_name,
		gpointer	be_data
	)

Register and lookup backend-specific data for this particular object

Definition at line 325 of file qofobject.c.

{
    GHashTable *ht;
    g_return_val_if_fail (object_is_initialized, FALSE);

    if (!type_name || *type_name == '\0' ||
        !backend_name || *backend_name == '\0' || !be_data)
        return FALSE;

    ht = g_hash_table_lookup (backend_data, backend_name);

    /* If it doesn't already exist, create a new table for this backend */
    if (!ht)
    {
        ht = g_hash_table_new (g_str_hash, g_str_equal);
        g_hash_table_insert (backend_data, (gchar *) backend_name, ht);
    }

    /* Now insert the data */
    g_hash_table_insert (ht, (gchar *) type_name, be_data);

    return TRUE;
}