Copyright | Will Thompson, Iñaki García Etxebarria and Jonas Platte |
---|---|
License | LGPL-2.1 |
Maintainer | Iñaki García Etxebarria (garetxe@gmail.com) |
Safe Haskell | None |
Language | Haskell2010 |
Provides a base class for implementing asynchronous function results.
Asynchronous operations are broken up into two separate operations
which are chained together by a AsyncReadyCallback
. To begin
an asynchronous operation, provide a AsyncReadyCallback
to the
asynchronous function. This callback will be triggered when the
operation has completed, and will be passed a 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, the 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 AsyncResult
) and returns the specific result that the
operation in question yields (e.g. a 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 AsyncReadyCallback
returns. You can pass
Nothing
for the AsyncReadyCallback
if you don't need to take any
action at all after the operation completes. Applications may also
take a reference to the AsyncResult
and call "_finish()
" later;
however, the "_finish()
" function may be called at most once.
Example of a typical asynchronous operation flow:
C code
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 IOErrorEnumCancelled
error.
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
PRIORITY_LOW
and PRIORITY_HIGH
, with PRIORITY_DEFAULT
as a default.
- newtype AsyncResult = AsyncResult (ManagedPtr AsyncResult)
- noAsyncResult :: Maybe AsyncResult
- class GObject o => IsAsyncResult o
- toAsyncResult :: IsAsyncResult o => o -> IO AsyncResult
- data AsyncResultGetSourceObjectMethodInfo
- asyncResultGetSourceObject :: (HasCallStack, MonadIO m, IsAsyncResult a) => a -> m Object
- data AsyncResultGetUserDataMethodInfo
- asyncResultGetUserData :: (HasCallStack, MonadIO m, IsAsyncResult a) => a -> m (Ptr ())
- data AsyncResultIsTaggedMethodInfo
- asyncResultIsTagged :: (HasCallStack, MonadIO m, IsAsyncResult a) => a -> Ptr () -> m Bool
- data AsyncResultLegacyPropagateErrorMethodInfo
- asyncResultLegacyPropagateError :: (HasCallStack, MonadIO m, IsAsyncResult a) => a -> m ()
Exported types
newtype AsyncResult Source #
GObject AsyncResult Source # | |
IsObject AsyncResult Source # | |
IsAsyncResult AsyncResult Source # | |
((~) * info (ResolveAsyncResultMethod t AsyncResult), MethodInfo * info AsyncResult p) => IsLabel t (AsyncResult -> p) Source # | |
((~) * info (ResolveAsyncResultMethod t AsyncResult), MethodInfo * info AsyncResult p) => IsLabelProxy t (AsyncResult -> p) Source # | |
HasAttributeList * AsyncResult Source # | |
type AttributeList AsyncResult Source # | |
type SignalList AsyncResult Source # | |
class GObject o => IsAsyncResult o Source #
toAsyncResult :: IsAsyncResult o => o -> IO AsyncResult Source #
Methods
getSourceObject
data AsyncResultGetSourceObjectMethodInfo Source #
((~) * signature (m Object), MonadIO m, IsAsyncResult a) => MethodInfo * AsyncResultGetSourceObjectMethodInfo a signature Source # | |
asyncResultGetSourceObject Source #
:: (HasCallStack, MonadIO m, IsAsyncResult a) | |
=> a |
|
-> m Object | Returns: a new reference to the source object for the |
Gets the source object from a AsyncResult
.
getUserData
data AsyncResultGetUserDataMethodInfo Source #
((~) * signature (m (Ptr ())), MonadIO m, IsAsyncResult a) => MethodInfo * AsyncResultGetUserDataMethodInfo a signature Source # | |
asyncResultGetUserData Source #
:: (HasCallStack, MonadIO m, IsAsyncResult a) | |
=> a |
|
-> m (Ptr ()) | Returns: the user data for |
Gets the user data from a AsyncResult
.
isTagged
data AsyncResultIsTaggedMethodInfo Source #
((~) * signature (Ptr () -> m Bool), MonadIO m, IsAsyncResult a) => MethodInfo * AsyncResultIsTaggedMethodInfo a signature Source # | |
:: (HasCallStack, MonadIO m, IsAsyncResult a) | |
=> a |
|
-> Ptr () |
|
-> m Bool | Returns: |
Checks if res
has the given sourceTag
(generally a function
pointer indicating the function res
was created by).
Since: 2.34
legacyPropagateError
data AsyncResultLegacyPropagateErrorMethodInfo Source #
((~) * signature (m ()), MonadIO m, IsAsyncResult a) => MethodInfo * AsyncResultLegacyPropagateErrorMethodInfo a signature Source # | |
asyncResultLegacyPropagateError Source #
:: (HasCallStack, MonadIO m, IsAsyncResult a) | |
=> a |
|
-> m () | (Can throw |
If res
is a SimpleAsyncResult
, this is equivalent to
simpleAsyncResultPropagateError
. Otherwise it returns
False
.
This can be used for legacy error handling in async *_finish()
wrapper functions that traditionally handled SimpleAsyncResult
error returns themselves rather than calling into the virtual method.
This should not be used in new code; AsyncResult
errors that are
set by virtual methods should also be extracted by virtual methods,
to enable subclasses to chain up correctly.
Since: 2.34