Struct gio::AsyncResult

source ·
#[repr(transparent)]
pub struct AsyncResult { /* private fields */ }
Expand description

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 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 GAsyncReadyCallback returns. You can pass None 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 AsyncResult and call “_finish()” later; however, the “_finish()” function may be called at most once.

Example of a typical asynchronous operation flow:

⚠️ The following code is in C ⚠️

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 IOErrorEnum::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.

Implements

AsyncResultExt

Implementations§

Trait Implementations§

Returns a copy of the value. Read more
Performs copy-assignment from source. Read more
Formats the value using the given formatter. Read more
Formats the value using the given formatter. Read more
Feeds this value into the given Hasher. Read more
Feeds a slice of this type into the given Hasher. Read more
This method returns an Ordering between self and other. Read more
Compares and returns the maximum of two values. Read more
Compares and returns the minimum of two values. Read more
Restrict a value to a certain interval. Read more
This method tests for self and other values to be equal, and is used by ==. Read more
This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason. Read more
This method returns an ordering between self and other values if one exists. Read more
This method tests less than (for self and other) and is used by the < operator. Read more
This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
This method tests greater than (for self and other) and is used by the > operator. Read more
This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more
Returns the type identifier of Self.

Auto Trait Implementations§

Blanket Implementations§

Gets the TypeId of self. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more
Upcasts an object to a superclass or interface T. Read more
Upcasts an object to a reference of its superclass or interface T. Read more
Tries to downcast to a subclass or interface implementor T. Read more
Tries to downcast to a reference of its subclass or interface implementor T. Read more
Tries to cast to an object of type T. This handles upcasting, downcasting and casting between interface and interface implementors. All checks are performed at runtime, while downcast and upcast will do many checks at compile-time already. Read more
Tries to cast to reference to an object of type T. This handles upcasting, downcasting and casting between interface and interface implementors. All checks are performed at runtime, while downcast and upcast will do many checks at compile-time already. Read more
Casts to T unconditionally. Read more
Casts to &T unconditionally. Read more

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

Returns true if the object is an instance of (can be cast to) T.
Returns the type of the object.
Returns the ObjectClass of the object. Read more
Returns the class of the object.
Returns the class of the object in the given type T. Read more
Returns the interface T of the object. Read more
Sets the property property_name of the object to value value. Read more
Sets the property property_name of the object to value value. Read more
Sets multiple properties of the object at once. Read more
Sets multiple properties of the object at once. Read more
Gets the property property_name of the object and cast it to the type V. Read more
Gets the property property_name of the object. Read more
Check if the object has a property property_name of the given type_. Read more
Get the type of the property property_name of this object. Read more
Get the ParamSpec of the property property_name of this object.
Return all ParamSpec of the properties of this object.
Freeze all property notifications until the return guard object is dropped. Read more
Set arbitrary data on this object with the given key. Read more
Return previously set arbitrary data of this object with the given key. Read more
Retrieve previously set arbitrary data of this object with the given key. Read more
Set arbitrary data on this object with the given key. Read more
Return previously set arbitrary data of this object with the given key. Read more
Retrieve previously set arbitrary data of this object with the given key. Read more
Block a given signal handler. Read more
Unblock a given signal handler.
Stop emission of the currently emitted signal.
Stop emission of the currently emitted signal by the (possibly detailed) signal name.
Connect to the signal signal_name on this object. Read more
Connect to the signal signal_id on this object. Read more
Connect to the signal signal_name on this object. Read more
Connect to the signal signal_id on this object. Read more
Connect to the signal signal_name on this object. Read more
Connect to the signal signal_id on this object. Read more
Connect a closure to the signal signal_name on this object. Read more
Connect a closure to the signal signal_id on this object. Read more
Limits the lifetime of closure to the lifetime of the object. When the object’s reference count drops to zero, the closure will be invalidated. An invalidated closure will ignore any calls to invoke_with_values, or invoke when using Rust closures. Read more
Emit signal by signal id. Read more
Same as Self::emit but takes Value for the arguments.
Emit signal by its name. Read more
Emit signal by its name. Read more
Emit signal by its name with details. Read more
Emit signal by its name with details. Read more
Emit signal by signal id with details. Read more
Emit signal by signal id with details. Read more
Disconnect a previously connected signal handler.
Connect to the notify signal of the object. Read more
Connect to the notify signal of the object. Read more
Connect to the notify signal of the object. Read more
Notify that the given property has changed its value. Read more
Notify that the given property has changed its value. Read more
Downgrade this object to a weak reference.
Add a callback to be notified when the Object is disposed.
Add a callback to be notified when the Object is disposed. Read more
Bind property source_property on this object to the target_property on the target object. Read more
Returns the strong reference count of this object.
Runs the dispose mechanism of the object. Read more
Ensures that the type has been registered with the type system.
The resulting type after obtaining ownership.
Creates owned data from borrowed data, usually by cloning. Read more
Uses borrowed data to replace owned data, usually by cloning. Read more
Converts the given value to a String. Read more
The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.