AsyncInitableIF

This is the asynchronous version of GInitable; it behaves the same in all ways except that initialization is asynchronous. For more details see the descriptions on GInitable

A class may implement both the GInitable and GAsyncInitable interfaces.

Users of objects implementing this are not intended to use the interface method directly; instead it will be used automatically in various ways. For C applications you generally just call g_async_initable_new_async() directly, or indirectly via a foo_thing_new_async() wrapper. This will call g_async_initable_init_async() under the cover, calling back with NULL and a set GError on failure.

A typical implementation might look something like this:

1 
2 enum {
3 NOT_INITIALIZED,
4 INITIALIZING,
5 INITIALIZED
6 };
7 
8 static void
9 _foo_ready_cb (Foo *self)
10 {
11 GList *l;
12 
13 self->priv->state = INITIALIZED;
14 
15 for (l = self->priv->init_results; l != NULL; l = l->next)
16 {
17 GTask *task = l->data;
18 
19 if (self->priv->success)
20 g_task_return_boolean (task, TRUE);
21 else
22 g_task_return_new_error (task, ...);
23 g_object_unref (task);
24 }
25 
26 g_list_free (self->priv->init_results);
27 self->priv->init_results = NULL;
28 }
29 
30 static void
31 foo_init_async (GAsyncInitable       *initable,
32 int                   io_priority,
33 GCancellable         *cancellable,
34 GAsyncReadyCallback   callback,
35 gpointer              user_data)
36 {
37 Foo *self = FOO (initable);
38 GTask *task;
39 
40 task = g_task_new (initable, cancellable, callback, user_data);
41 
42 switch (self->priv->state)
43 {
44 case NOT_INITIALIZED:
45 _foo_get_ready (self);
46 self->priv->init_results = g_list_append (self->priv->init_results,
47 task);
48 self->priv->state = INITIALIZING;
49 break;
50 case INITIALIZING:
51 self->priv->init_results = g_list_append (self->priv->init_results,
52 task);
53 break;
54 case INITIALIZED:
55 if (!self->priv->success)
56 g_task_return_new_error (task, ...);
57 else
58 g_task_return_boolean (task, TRUE);
59 g_object_unref (task);
60 break;
61 }
62 }
63 
64 static gboolean
65 foo_init_finish (GAsyncInitable       *initable,
66 GAsyncResult         *result,
67 GError              **error)
68 {
69 g_return_val_if_fail (g_task_is_valid (result, initable), FALSE);
70 
71 return g_task_propagate_boolean (G_TASK (result), error);
72 }
73 
74 static void
75 foo_async_initable_iface_init (gpointer g_iface,
76 gpointer data)
77 {
78 GAsyncInitableIface *iface = g_iface;
79 
80 iface->init_async = foo_init_async;
81 iface->init_finish = foo_init_finish;
82 }