Interface
GioAsyncResult
since: 2.0
Description
interface Gio.AsyncResult : GObject.Object
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][g-main-context-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 GFileEnumerator
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:
void _theoretical_frobnitz_async (Theoretical *t,
GCancellable *c,
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 # {#io-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.
Available since: 2.0
Prerequisite
In order to implement AsyncResult, your type must inherit fromGObject
.
Instance methods
g_async_result_is_tagged
Checks if res
has the given source_tag
(generally a function
pointer indicating the function res
was created by).
since: 2.34
g_async_result_legacy_propagate_error
If res
is a GSimpleAsyncResult
, this is equivalent to
g_simple_async_result_propagate_error(). Otherwise it returns
FALSE
.
since: 2.34
Interface structure
struct GioAsyncResultIface {
GTypeInterface g_iface;
gpointer (* get_user_data) (
GAsyncResult* res
);
GObject* (* get_source_object) (
GAsyncResult* res
);
gboolean (* is_tagged) (
GAsyncResult* res,
gpointer source_tag
);
}
Interface definition for GAsyncResult
.
Interface members
g_iface |
|
The parent interface. |
|
get_user_data |
|
No description available. | |
get_source_object |
|
No description available. | |
is_tagged |
|
No description available. |
Virtual methods
Gio.AsyncResult.is_tagged
Checks if res
has the given source_tag
(generally a function
pointer indicating the function res
was created by).
since: 2.34