class: AsyncResult

[52:7] extends: object

GAsyncResult provides a base class for implementing asynchronous function results. Asynchronous operations are broken up into two separate operations which are chained together by a GAsyncReadyCallback. To begin an asynchronous operation, provide a GAsyncReadyCallback to the asynchronous function. This callback will be triggered when the operation has completed, and must be run in a later iteration of the thread-default main context (see [method@GLib.MainContext.push_thread_default]) from where the operation was initiated. It will be passed a GAsyncResult instance filled with the details of the operation's success or failure, the object the asynchronous function was started for and any error codes returned. The asynchronous callback function is then expected to call the corresponding _finish() function, passing the object the function was called for, the GAsyncResult instance, and (optionally) an @error to grab any error conditions that may have occurred. The _finish() function for an operation takes the generic result (of type GAsyncResult) and returns the specific result that the operation in question yields (e.g. a [class@Gio.FileEnumerator] for a "enumerate children" operation). If the result or error status of the operation is not needed, there is no need to call the _finish() function; GIO will take care of cleaning up the result and error information after the GAsyncReadyCallback returns. You can pass NULL for the GAsyncReadyCallback if you don't need to take any action at all after the operation completes. Applications may also take a reference to the GAsyncResult and call _finish() later; however, the _finish() function may be called at most once. Example of a typical asynchronous operation flow:

GAsyncReadyCallback cb, gpointer u); gboolean _theoretical_frobnitz_finish
(Theoretical *t, GAsyncResult *res, GError **e); static void
frobnitz_result_func (GObject *source_object, GAsyncResult *res, gpointer
user_data) { gboolean success = FALSE; success = _theoretical_frobnitz_finish
(source_object, res, NULL); if (success) g_printf ("Hurray!\n"); else
g_printf ("Uh oh!\n"); ... } int main (int argc, void *argv[]) { ...
_theoretical_frobnitz_async (theoretical_data, NULL, frobnitz_result_func,
NULL); ... } ``` The callback for an asynchronous operation is called only
once, and is always called, even in the case of a cancelled operation. On
cancellation the result is a `G_IO_ERROR_CANCELLED` error. ## I/O Priority
Many I/O-related asynchronous operations have a priority parameter, which is
used in certain cases to determine the order in which operations are
executed. They are not used to determine system-wide I/O scheduling.
Priorities are integers, with lower numbers indicating higher priority. It is
recommended to choose priorities between `G_PRIORITY_LOW` and
`G_PRIORITY_HIGH`, with `G_PRIORITY_DEFAULT` as a default.

#### Members
- **handleObj**
- **lib**
- **retainedCallbacks**
- **signalHandlerNames**
- **signalSetterHandlers**

#### Methods

- **AsyncResult** (`Handle = null`)

	> Creates a new `AsyncResult` by wrapping a native handle or another wrapper.

	- **@p** `Handle` is the native handle or another wrapper whose handle to adopt.


- **toNativeHandle** (`Source`)

	> Normalizes a constructor argument into a raw pointer carrier. Accepts a raw NativeHandle, a raw NativeBuffer returned from `fn.call(...)`, another generated wrapper exposing `handle()`, or null. Returns null when the argument carries no pointer.

	- **@p** `Source` is the raw handle, raw buffer, wrapper, or null.
	- **@r** `A` raw pointer carrier or null when no pointer is present.


- **getLib** ()

	> Returns the opened native library for this generated wrapper.

	- **@r** `The` opened native library.


- **handle** ()

	> Returns the wrapped NativeHandle.

	- **@r** `The` wrapped NativeHandle.


- **isNull** ()

	> Returns true when the wrapped handle is null.

	- **@r** `A` bool.


- **describe** ()

	> Returns a small string for debugging generated wrappers.

	- **@r** `A` string.


- **get\_source\_object** ()

	> Gets the source object from a [iface@Gio.AsyncResult].



- **get\_user\_data** ()

	> Gets the user data from a [iface@Gio.AsyncResult].



- **is\_tagged** (`source_tag`)

	> Checks if @res has the given @source_tag (generally a function pointer indicating the function @res was created by).

	- **@p** `source_tag` is an application-defined tag.


- **legacy\_propagate\_error** ()

	> If @res is a [class@Gio.SimpleAsyncResult], this is equivalent to [method@Gio.SimpleAsyncResult.propagate_error]. Otherwise it returns `FALSE`. This can be used for legacy error handling in async `*_finish()` wrapper functions that traditionally handled [class@Gio.SimpleAsyncResult] error returns themselves rather than calling into the virtual method. This should not be used in new code; [iface@Gio.AsyncResult] errors that are set by virtual methods should also be extracted by virtual methods, to enable subclasses to chain up correctly.