Gio.AsyncResult¶
- Implementations
Methods¶
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Virtual Methods¶
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Properties¶
None
Signals¶
None
Fields¶
None
Class Details¶
- class Gio.AsyncResult¶
- Bases
- Structure
Provides a base class for implementing asynchronous function results.
Asynchronous operations are broken up into two separate operations which are chained together by a
Gio.AsyncReadyCallback
. To begin an asynchronous operation, provide aGio.AsyncReadyCallback
to the asynchronous function. This callback will be triggered when the operation has completed, and must be run in a later iteration of thethread-default main context
from where the operation was initiated. It will be passed aGio.AsyncResult
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, theGio.AsyncResult
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
Gio.AsyncResult
) and returns the specific result that the operation in question yields (e.g. aGio.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 theGio.AsyncReadyCallback
returns. You can passNone
for theGio.AsyncReadyCallback
if you don’t need to take any action at all after the operation completes. Applications may also take a reference to theGio.AsyncResult
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
Gio.IOErrorEnum.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
GLib.PRIORITY_LOW
andGLib.PRIORITY_HIGH
, withGLib.PRIORITY_DEFAULT
as a default.- get_source_object()[source]¶
- Returns
a new reference to the source object for the self, or
None
if there is none.- Return type
Gets the source object from a
Gio.AsyncResult
.
- get_user_data()[source]¶
-
Gets the user data from a
Gio.AsyncResult
.
- is_tagged(source_tag)[source]¶
- Parameters
- Returns
- Return type
Checks if self has the given source_tag (generally a function pointer indicating the function self was created by).
New in version 2.34.
- legacy_propagate_error()[source]¶
- Raises
- Returns
True
if error is has been filled in with an error from self,False
if not.- Return type
If self is a
Gio.SimpleAsyncResult
, this is equivalent toGio.SimpleAsyncResult.propagate_error
(). Otherwise it returnsFalse
.This can be used for legacy error handling in async *_finish() wrapper functions that traditionally handled
Gio.SimpleAsyncResult
error returns themselves rather than calling into the virtual method. This should not be used in new code;Gio.AsyncResult
errors that are set by virtual methods should also be extracted by virtual methods, to enable subclasses to chain up correctly.New in version 2.34.
- do_get_source_object() virtual¶
- Returns
a new reference to the source object for the res, or
None
if there is none.- Return type
Gets the source object from a
Gio.AsyncResult
.
- do_get_user_data() virtual¶
-
Gets the user data from a
Gio.AsyncResult
.
- do_is_tagged(source_tag) virtual¶
- Parameters
- Returns
- Return type
Checks if res has the given source_tag (generally a function pointer indicating the function res was created by).
New in version 2.34.