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Gio.AsyncInitable

interface

GAsyncInitable is an interface for asynchronously initializable objects.

This is the asynchronous version of Initable; 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 AsyncInitable.new_async directly, or indirectly via a foo_thing_new_async() wrapper. This will call AsyncInitable.init_async under the covers, calling back with NULL and a set GError on failure.

A typical implementation might look something like this:

enum {
   NOT_INITIALIZED,
   INITIALIZING,
   INITIALIZED
};

static void
_foo_ready_cb (Foo *self)
{
  GList *l;

  self->priv->state = INITIALIZED;

  for (l = self->priv->init_results; l != NULL; l = l->next)
    {
      GTask *task = l->data;

      if (self->priv->success)
        g_task_return_boolean (task, TRUE);
      else
        g_task_return_new_error (task, ...);
      g_object_unref (task);
    }

  g_list_free (self->priv->init_results);
  self->priv->init_results = NULL;
}

static void
foo_init_async (GAsyncInitable       *initable,
                int                   io_priority,
                GCancellable         *cancellable,
                GAsyncReadyCallback   callback,
                gpointer              user_data)
{
  Foo *self = FOO (initable);
  GTask *task;

  task = g_task_new (initable, cancellable, callback, user_data);
  g_task_set_name (task, G_STRFUNC);

  switch (self->priv->state)
    {
      case NOT_INITIALIZED:
        _foo_get_ready (self);
        self->priv->init_results = g_list_append (self->priv->init_results,
                                                  task);
        self->priv->state = INITIALIZING;
        break;
      case INITIALIZING:
        self->priv->init_results = g_list_append (self->priv->init_results,
                                                  task);
        break;
      case INITIALIZED:
        if (!self->priv->success)
          g_task_return_new_error (task, ...);
        else
          g_task_return_boolean (task, TRUE);
        g_object_unref (task);
        break;
    }
}

static gboolean
foo_init_finish (GAsyncInitable       *initable,
                 GAsyncResult         *result,
                 GError              **error)
{
  g_return_val_if_fail (g_task_is_valid (result, initable), FALSE);

  return g_task_propagate_boolean (G_TASK (result), error);
}

static void
foo_async_initable_iface_init (gpointer g_iface,
                               gpointer data)
{
  GAsyncInitableIface *iface = g_iface;

  iface->init_async = foo_init_async;
  iface->init_finish = foo_init_finish;
}

Methods

init_async

def init_async(self, io_priority: int, cancellable: Cancellable | None = ..., callback: Callable[[AsyncInitable | None, AsyncResult], None] | None = ...) -> None

Starts asynchronous initialization of the object implementing the interface. This must be done before any real use of the object after initial construction. If the object also implements Initable you can optionally call Initable.init instead.

This method is intended for language bindings. If writing in C, g_async_initable_new_async() should typically be used instead.

When the initialization is finished, callback will be called. You can then call AsyncInitable.init_finish to get the result of the initialization.

Implementations may also support cancellation. If cancellable is not None, then initialization can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error IOErrorEnum.CANCELLED will be returned. If cancellable is not None, and the object doesn't support cancellable initialization, the error IOErrorEnum.NOT_SUPPORTED will be returned.

As with Initable, if the object is not initialized, or initialization returns with an error, then all operations on the object except GObject.Object.ref and GObject.Object.unref are considered to be invalid, and have undefined behaviour. They will often fail with g_critical() or g_warning(), but this must not be relied on.

Callers should not assume that a class which implements AsyncInitable can be initialized multiple times; for more information, see Initable.init. If a class explicitly supports being initialized multiple times, implementation requires yielding all subsequent calls to init_async() on the results of the first call.

For classes that also support the Initable interface, the default implementation of this method will run the Initable.init function in a thread, so if you want to support asynchronous initialization via threads, just implement the AsyncInitable interface without overriding any interface methods.

Parameters:

  • io_priority — the I/O priority of the operation
  • cancellable — optional Cancellable object, None to ignore.
  • callback — a GAsyncReadyCallback to call when the request is satisfied

init_finish

def init_finish(self, res: AsyncResult) -> bool

Finishes asynchronous initialization and returns the result. See AsyncInitable.init_async.

Parameters:

new_finish

def new_finish(self, res: AsyncResult) -> GObject.Object

Finishes the async construction for the various g_async_initable_new calls, returning the created object or None on error.

Parameters:

Static functions

newv_async

@staticmethod
def newv_async(object_type: type | GObject.Type, n_parameters: int, parameters: GObject.Parameter, io_priority: int, cancellable: Cancellable | None = ..., callback: AsyncReadyCallback | None = ...) -> None

:::warning Deprecated since 2.54 This API is deprecated. :::

Helper function for constructing AsyncInitable object. This is similar to GObject.Object.newv but also initializes the object asynchronously.

When the initialization is finished, callback will be called. You can then call AsyncInitable.new_finish to get the new object and check for any errors.

Parameters:

  • object_type — a GType supporting AsyncInitable.
  • n_parameters — the number of parameters in parameters
  • parameters — the parameters to use to construct the object
  • io_priority — the I/O priority of the operation
  • cancellable — optional Cancellable object, None to ignore.
  • callback — a GAsyncReadyCallback to call when the initialization is finished

Virtual methods

do_init_async

def do_init_async(self, io_priority: int, cancellable: Cancellable | None = ..., callback: Callable[[AsyncInitable | None, AsyncResult], None] | None = ...) -> None

Starts asynchronous initialization of the object implementing the interface. This must be done before any real use of the object after initial construction. If the object also implements Initable you can optionally call Initable.init instead.

This method is intended for language bindings. If writing in C, g_async_initable_new_async() should typically be used instead.

When the initialization is finished, callback will be called. You can then call AsyncInitable.init_finish to get the result of the initialization.

Implementations may also support cancellation. If cancellable is not None, then initialization can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error IOErrorEnum.CANCELLED will be returned. If cancellable is not None, and the object doesn't support cancellable initialization, the error IOErrorEnum.NOT_SUPPORTED will be returned.

As with Initable, if the object is not initialized, or initialization returns with an error, then all operations on the object except GObject.Object.ref and GObject.Object.unref are considered to be invalid, and have undefined behaviour. They will often fail with g_critical() or g_warning(), but this must not be relied on.

Callers should not assume that a class which implements AsyncInitable can be initialized multiple times; for more information, see Initable.init. If a class explicitly supports being initialized multiple times, implementation requires yielding all subsequent calls to init_async() on the results of the first call.

For classes that also support the Initable interface, the default implementation of this method will run the Initable.init function in a thread, so if you want to support asynchronous initialization via threads, just implement the AsyncInitable interface without overriding any interface methods.

Parameters:

  • io_priority — the I/O priority of the operation
  • cancellable — optional Cancellable object, None to ignore.
  • callback — a GAsyncReadyCallback to call when the request is satisfied

do_init_finish

def do_init_finish(self, res: AsyncResult) -> bool

Finishes asynchronous initialization and returns the result. See AsyncInitable.init_async.

Parameters: