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GObject.Object
parent-child marker Gio.SimpleAsyncResult

Class Gio.SimpleAsyncResult

Import line: Gio = imports.gi.Gio;
GIR File: Gio-2.0.gir
C documentation: GSimpleAsyncResult
Class : SimpleAsyncResult
Implements: Gio.AsyncResult
Extends: GObject.Object
Implements GAsyncResult for simple cases. Most of the time, this
will be all an application needs, and will be used transparently.
Because of this, GSimpleAsyncResult is used throughout GIO for
handling asynchronous functions.
GSimpleAsyncResult handles GAsyncReadyCallbacks, error
reporting, operation cancellation and the final state of an operation,
completely transparent to the application. Results can be returned
as a pointer e.g. for functions that return data that is collected
asynchronously, a boolean value for checking the success or failure
of an operation, or a gssize for operations which return the number
of bytes modified by the operation; all of the simple return cases
are covered.
Most of the time, an application will not need to know of the details
of this API; it is handled transparently, and any necessary operations
are handled by GAsyncResult's interface. However, if implementing a
new GIO module, for writing language bindings, or for complex
applications that need better control of how asynchronous operations
are completed, it is important to understand this functionality.
GSimpleAsyncResults are tagged with the calling function to ensure
that asynchronous functions and their finishing functions are used
together correctly.
To create a new GSimpleAsyncResult, call g_simple_async_result_new().
If the result needs to be created for a GError, use
g_simple_async_result_new_from_error() or
g_simple_async_result_new_take_error(). If a GError is not available
(e.g. the asynchronous operation's doesn't take a GError argument),
but the result still needs to be created for an error condition, use
g_simple_async_result_new_error() (or g_simple_async_result_set_error_va()
if your application or binding requires passing a variable argument list
directly), and the error can then be propagated through the use of
g_simple_async_result_propagate_error().
An asynchronous operation can be made to ignore a cancellation event by
calling g_simple_async_result_set_handle_cancellation() with a
GSimpleAsyncResult for the operation and FALSE. This is useful for
operations that are dangerous to cancel, such as close (which would
cause a leak if cancelled before being run).
GSimpleAsyncResult can integrate into GLib's event loop, GMainLoop,
or it can use GThreads if available.
g_simple_async_result_complete() will finish an I/O task directly
from the point where it is called. g_simple_async_result_complete_in_idle()
will finish it from an idle handler in the linkend="g-main-context-push-thread-default">thread-default main
context. g_simple_async_result_run_in_thread() will run the
job in a separate thread and then deliver the result to the
thread-default main context.
To set the results of an asynchronous function,
g_simple_async_result_set_op_res_gpointer(),
g_simple_async_result_set_op_res_gboolean(), and
g_simple_async_result_set_op_res_gssize()
are provided, setting the operation's result to a gpointer, gboolean, or
gssize, respectively.
Likewise, to get the result of an asynchronous function,
g_simple_async_result_get_op_res_gpointer(),
g_simple_async_result_get_op_res_gboolean(), and
g_simple_async_result_get_op_res_gssize() are
provided, getting the operation's result as a gpointer, gboolean, and
gssize, respectively.
For the details of the requirements implementations must respect, see
GAsyncResult. A typical implementation of an asynchronous operation
using GSimpleAsyncResult looks something like this:
|[
static void
baked_cb (Cake *cake,
gpointer user_data)
{
/* In this example, this callback is not given a reference to the cake, so
* the GSimpleAsyncResult has to take a reference to it.
*/
GSimpleAsyncResult *result = user_data;
if (cake == NULL)
g_simple_async_result_set_error (result,
BAKER_ERRORS,
BAKER_ERROR_NO_FLOUR,
"Go to the supermarket");
else
g_simple_async_result_set_op_res_gpointer (result,
g_object_ref (cake),
g_object_unref);
/* In this example, we assume that baked_cb is called as a callback from
* the mainloop, so it's safe to complete the operation synchronously here.
* If, however, _baker_prepare_cake () might call its callback without
* first returning to the mainloop — inadvisable, but some APIs do so —
* we would need to use g_simple_async_result_complete_in_idle().
*/
g_simple_async_result_complete (result);
g_object_unref (result);
}
void
baker_bake_cake_async (Baker *self,
guint radius,
GAsyncReadyCallback callback,
gpointer user_data)
{
GSimpleAsyncResult *simple;
Cake *cake;
if (radius < 3)
{
g_simple_async_report_error_in_idle (G_OBJECT (self),
callback,
user_data,
BAKER_ERRORS,
BAKER_ERROR_TOO_SMALL,
"ucm radius cakes are silly",
radius);
return;
}
simple = g_simple_async_result_new (G_OBJECT (self),
callback,
user_data,
baker_bake_cake_async);
cake = _baker_get_cached_cake (self, radius);
if (cake != NULL)
{
g_simple_async_result_set_op_res_gpointer (simple,
g_object_ref (cake),
g_object_unref);
g_simple_async_result_complete_in_idle (simple);
g_object_unref (simple);
/* Drop the reference returned by _baker_get_cached_cake(); the
* GSimpleAsyncResult has taken its own reference.
*/
g_object_unref (cake);
return;
}
_baker_prepare_cake (self, radius, baked_cb, simple);
}
Cake *
baker_bake_cake_finish (Baker *self,
GAsyncResult *result,
GError **error)
{
GSimpleAsyncResult *simple;
Cake *cake;
g_return_val_if_fail (g_simple_async_result_is_valid (result,
G_OBJECT (self),
baker_bake_cake_async),
NULL);
simple = (GSimpleAsyncResult *) result;
if (g_simple_async_result_propagate_error (simple, error))
return NULL;
cake = CAKE (g_simple_async_result_get_op_res_gpointer (simple));
return g_object_ref (cake);
}
]|
Properties
None
Methods / Constructors
Method / Constructor Defined By
 
new Gio.SimpleAsyncResult ()
Create a new Gio.SimpleAsyncResult
Create a new Gio.SimpleAsyncResult
 
Events
None
Used by These Methods / Signals / Properties- Nowhere other than here
Documentation generated by Introspection Doc Generator Loosely Based on JsDoc Toolkit on Sat Apr 16 2011 17:11:16 GMT+0800 (HKT)