gi-gio-2.0.38: Gio bindings

Copyright | Will Thompson and Iñaki García Etxebarria
License | LGPL-2.1
Maintainer | Iñaki García Etxebarria
Safe Haskell | None
Language | Haskell2010

GI.Gio.Objects.SimpleAsyncResult

Contents

- Exported types
- Methods
  - complete
  - completeInIdle
  - getOpResGboolean
  - getOpResGssize
  - isValid
  - new
  - newFromError
  - propagateError
  - setCheckCancellable
  - setFromError
  - setHandleCancellation
  - setOpResGboolean
  - setOpResGssize

Description

As of GLib 2.46, `GSimpleAsyncResult` is deprecated in favor of `Task`, which provides a simpler API.

`GSimpleAsyncResult` implements `AsyncResult`.

`GSimpleAsyncResult` handles [type`gio`.AsyncReadyCallback]s, 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 `AsyncResult`’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.

`GSimpleAsyncResult`s 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 `simpleAsyncResultNew`. If the result needs to be created for a `GError`, use `simpleAsyncResultNewFromError` or `SimpleAsyncResult`.`new_take_error`(). If a `GError` is not available (e.g. the asynchronous operation doesn’t take a `GError` argument), but the result still needs to be created for an error condition, use `SimpleAsyncResult`.`new_error`() (or `SimpleAsyncResult`.`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 `simpleAsyncResultPropagateError`.

An asynchronous operation can be made to ignore a cancellation event by calling `simpleAsyncResultSetHandleCancellation` 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, [type`gLib`.MainLoop], or it can use [type`gLib`.Thread]s. `simpleAsyncResultComplete` will finish an I/O task directly from the point where it is called. `simpleAsyncResultCompleteInIdle` will finish it from an idle handler in the thread-default main context (see `mainContextPushThreadDefault`) where the `GSimpleAsyncResult` was created. `SimpleAsyncResult`.`run_in_thread`() will run the job in a separate thread and then use `simpleAsyncResultCompleteInIdle` to deliver the result.

To set the results of an asynchronous function, `SimpleAsyncResult`.`set_op_res_gpointer`(), `simpleAsyncResultSetOpResGboolean`, and `simpleAsyncResultSetOpResGssize` are provided, setting the operation's result to a `gpointer`, `gboolean`, or `gssize`, respectively.

Likewise, to get the result of an asynchronous function, `SimpleAsyncResult`.`get_op_res_gpointer`(), `simpleAsyncResultGetOpResGboolean`, and `simpleAsyncResultGetOpResGssize` are provided, getting the operation’s result as a `gpointer`, `gboolean`, and `gssize`, respectively.

For the details of the requirements implementations must respect, see `AsyncResult`. A typical implementation of an asynchronous operation using `GSimpleAsyncResult` looks something like this:

### c code

    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);
    }

Synopsis

- newtype SimpleAsyncResult = SimpleAsyncResult (ManagedPtr SimpleAsyncResult)
- class (GObject o, IsDescendantOf SimpleAsyncResult o) => IsSimpleAsyncResult o
- toSimpleAsyncResult :: (MonadIO m, IsSimpleAsyncResult o) => o -> m SimpleAsyncResult
- simpleAsyncResultComplete :: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) => a -> m ()
- simpleAsyncResultCompleteInIdle :: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) => a -> m ()
- simpleAsyncResultGetOpResGboolean :: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) => a -> m Bool
- simpleAsyncResultGetOpResGssize :: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) => a -> m Int64
- simpleAsyncResultIsValid :: (HasCallStack, MonadIO m, IsAsyncResult a, IsObject b) => a -> Maybe b -> Ptr () -> m Bool
- simpleAsyncResultNew :: (HasCallStack, MonadIO m, IsObject a) => Maybe a -> Maybe AsyncReadyCallback -> Ptr () -> m SimpleAsyncResult
- simpleAsyncResultNewFromError :: (HasCallStack, MonadIO m, IsObject a) => Maybe a -> Maybe AsyncReadyCallback -> GError -> m SimpleAsyncResult
- simpleAsyncResultPropagateError :: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) => a -> m ()
- simpleAsyncResultSetCheckCancellable :: (HasCallStack, MonadIO m, IsSimpleAsyncResult a, IsCancellable b) => a -> Maybe b -> m ()
- simpleAsyncResultSetFromError :: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) => a -> GError -> m ()
- simpleAsyncResultSetHandleCancellation :: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) => a -> Bool -> m ()
- simpleAsyncResultSetOpResGboolean :: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) => a -> Bool -> m ()
- simpleAsyncResultSetOpResGssize :: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) => a -> Int64 -> m ()

# Exported types

newtype SimpleAsyncResult Source #

Memory-managed wrapper type.

Constructors

SimpleAsyncResult (ManagedPtr SimpleAsyncResult) |

#### Instances

Instances details

Eq SimpleAsyncResult Source # |
Instance details Defined in GI.Gio.Objects.SimpleAsyncResult Methods (==) :: SimpleAsyncResult -> SimpleAsyncResult -> Bool Source # (/=) :: SimpleAsyncResult -> SimpleAsyncResult -> Bool Source #
GObject SimpleAsyncResult Source # |
Instance details Defined in GI.Gio.Objects.SimpleAsyncResult
ManagedPtrNewtype SimpleAsyncResult Source # |
Instance details Defined in GI.Gio.Objects.SimpleAsyncResult Methods toManagedPtr :: SimpleAsyncResult -> ManagedPtr SimpleAsyncResult Source #
TypedObject SimpleAsyncResult Source # |
Instance details Defined in GI.Gio.Objects.SimpleAsyncResult Methods glibType :: IO GType Source #
HasParentTypes SimpleAsyncResult Source # |
Instance details Defined in GI.Gio.Objects.SimpleAsyncResult
IsGValue (Maybe SimpleAsyncResult) Source # | Convert `SimpleAsyncResult` to and from `GValue`. See `toGValue` and `fromGValue`.
Instance details Defined in GI.Gio.Objects.SimpleAsyncResult Methods gvalueGType_ :: IO GType Source # gvalueSet_ :: Ptr GValue -> Maybe SimpleAsyncResult -> IO () Source # gvalueGet_ :: Ptr GValue -> IO (Maybe SimpleAsyncResult) Source #
type ParentTypes SimpleAsyncResult Source # |
Instance details Defined in GI.Gio.Objects.SimpleAsyncResult type ParentTypes SimpleAsyncResult = '[Object, AsyncResult]

class (GObject o, IsDescendantOf SimpleAsyncResult o) => IsSimpleAsyncResult o Source #

Type class for types which can be safely cast to `SimpleAsyncResult`, for instance with `toSimpleAsyncResult`.

#### Instances

Instances details

(GObject o, IsDescendantOf SimpleAsyncResult o) => IsSimpleAsyncResult o Source # |
Instance details Defined in GI.Gio.Objects.SimpleAsyncResult

toSimpleAsyncResult :: (MonadIO m, IsSimpleAsyncResult o) => o -> m SimpleAsyncResult Source #

Cast to `SimpleAsyncResult`, for types for which this is known to be safe. For general casts, use `castTo`.

# Methods

### Click to display all available methods, including inherited ones

Expand

#### Methods

bindProperty, bindPropertyFull, complete, completeInIdle, forceFloating, freezeNotify, getv, isFloating, isTagged, legacyPropagateError, notify, notifyByPspec, propagateError, ref, refSink, runDispose, stealData, stealQdata, thawNotify, unref, watchClosure.

#### Getters

getData, getOpResGboolean, getOpResGssize, getProperty, getQdata, getSourceObject, getUserData.

#### Setters

setCheckCancellable, setData, setDataFull, setFromError, setHandleCancellation, setOpResGboolean, setOpResGssize, setProperty.

## complete

simpleAsyncResultComplete Source #

Arguments

:: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) |
=> a | `simple`: a `SimpleAsyncResult`.
-> m () |

Deprecated: (Since version 2.46)Use `Task` instead.

Completes an asynchronous I/O job immediately. Must be called in the thread where the asynchronous result was to be delivered, as it invokes the callback directly. If you are in a different thread use `simpleAsyncResultCompleteInIdle`.

Calling this function takes a reference to `simple` for as long as is needed to complete the call.

## completeInIdle

simpleAsyncResultCompleteInIdle Source #

Arguments

:: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) |
=> a | `simple`: a `SimpleAsyncResult`.
-> m () |

Deprecated: (Since version 2.46)Use `Task` instead.

Completes an asynchronous function in an idle handler in the thread-default main context (see `mainContextPushThreadDefault`) of the thread that `simple` was initially created in (and re-pushes that context around the invocation of the callback).

Calling this function takes a reference to `simple` for as long as is needed to complete the call.

## getOpResGboolean

simpleAsyncResultGetOpResGboolean Source #

Arguments

:: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) |
=> a | `simple`: a `SimpleAsyncResult`.
-> m Bool | Returns: `True` if the operation's result was `True`, `False` if the operation's result was `False`.

Deprecated: (Since version 2.46)Use `Task` and `taskPropagateBoolean` instead.

Gets the operation result boolean from within the asynchronous result.

## getOpResGssize

simpleAsyncResultGetOpResGssize Source #

Arguments

:: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) |
=> a | `simple`: a `SimpleAsyncResult`.
-> m Int64 | Returns: a gssize returned from the asynchronous function.

Deprecated: (Since version 2.46)Use `Task` and `taskPropagateInt` instead.

Gets a gssize from the asynchronous result.

## isValid

simpleAsyncResultIsValid Source #

Arguments

:: (HasCallStack, MonadIO m, IsAsyncResult a, IsObject b) |
=> a | `result`: the `AsyncResult` passed to the _finish function.
-> Maybe b | `source`: the `Object` passed to the _finish function.
-> Ptr () | `sourceTag`: the asynchronous function.
-> m Bool | Returns: `TRUE` if all checks passed or `FALSE` if any failed.

Deprecated: (Since version 2.46)Use `Task` and `taskIsValid` instead.

Ensures that the data passed to the _finish function of an async operation is consistent. Three checks are performed.

First, `result` is checked to ensure that it is really a `SimpleAsyncResult`. Second, `source` is checked to ensure that it matches the source object of `result`. Third, `sourceTag` is checked to ensure that it is equal to the `sourceTag` argument given to `simpleAsyncResultNew` (which, by convention, is a pointer to the _async function corresponding to the _finish function from which this function is called). (Alternatively, if either `sourceTag` or `result`'s source tag is `Nothing`, then the source tag check is skipped.)

Since: 2.20

## new

simpleAsyncResultNew Source #

Arguments

:: (HasCallStack, MonadIO m, IsObject a) |
=> Maybe a | `sourceObject`: a `Object`, or `Nothing`.
-> Maybe AsyncReadyCallback | `callback`: a `AsyncReadyCallback`.
-> Ptr () | `sourceTag`: the asynchronous function.
-> m SimpleAsyncResult | Returns: a `SimpleAsyncResult`.

Deprecated: (Since version 2.46)Use `taskNew` instead.

Creates a `SimpleAsyncResult`.

The common convention is to create the `SimpleAsyncResult` in the function that starts the asynchronous operation and use that same function as the `sourceTag`.

If your operation supports cancellation with `Cancellable` (which it probably should) then you should provide the user's cancellable to `simpleAsyncResultSetCheckCancellable` immediately after this function returns.

## newFromError

simpleAsyncResultNewFromError Source #

Arguments

:: (HasCallStack, MonadIO m, IsObject a) |
=> Maybe a | `sourceObject`: a `Object`, or `Nothing`.
-> Maybe AsyncReadyCallback | `callback`: a `AsyncReadyCallback`.
-> GError | `error`: a `GError`
-> m SimpleAsyncResult | Returns: a `SimpleAsyncResult`.

Deprecated: (Since version 2.46)Use `taskNew` and `taskReturnError` instead.

Creates a `SimpleAsyncResult` from an error condition.

## propagateError

simpleAsyncResultPropagateError Source #

Arguments

:: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) |
=> a | `simple`: a `SimpleAsyncResult`.
-> m () | (Can throw `GError`)

Deprecated: (Since version 2.46)Use `Task` instead.

Propagates an error from within the simple asynchronous result to a given destination.

If the `Cancellable` given to a prior call to `simpleAsyncResultSetCheckCancellable` is cancelled then this function will return `True` with `dest` set appropriately.

## setCheckCancellable

simpleAsyncResultSetCheckCancellable Source #

Arguments

:: (HasCallStack, MonadIO m, IsSimpleAsyncResult a, IsCancellable b) |
=> a | `simple`: a `SimpleAsyncResult`
-> Maybe b | `checkCancellable`: a `Cancellable` to check, or `Nothing` to unset
-> m () |

Deprecated: (Since version 2.46)Use `Task` instead.

Sets a `Cancellable` to check before dispatching results.

This function has one very specific purpose: the provided cancellable is checked at the time of `simpleAsyncResultPropagateError` If it is cancelled, these functions will return an "Operation was cancelled" error (`IOErrorEnumCancelled`).

Implementors of cancellable asynchronous functions should use this in order to provide a guarantee to their callers that cancelling an async operation will reliably result in an error being returned for that operation (even if a positive result for the operation has already been sent as an idle to the main context to be dispatched).

The checking described above is done regardless of any call to the unrelated `simpleAsyncResultSetHandleCancellation` function.

Since: 2.32

## setFromError

simpleAsyncResultSetFromError Source #

Arguments

:: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) |
=> a | `simple`: a `SimpleAsyncResult`.
-> GError | `error`: `GError`.
-> m () |

Deprecated: (Since version 2.46)Use `Task` and `taskReturnError` instead.

Sets the result from a `GError`.

## setHandleCancellation

simpleAsyncResultSetHandleCancellation Source #

Arguments

:: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) |
=> a | `simple`: a `SimpleAsyncResult`.
-> Bool | `handleCancellation`: a `Bool`.
-> m () |

Deprecated: (Since version 2.46)

Sets whether to handle cancellation within the asynchronous operation.

This function has nothing to do with `simpleAsyncResultSetCheckCancellable`. It only refers to the `Cancellable` passed to `g_simple_async_result_run_in_thread()`.

## setOpResGboolean

simpleAsyncResultSetOpResGboolean Source #

Arguments

:: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) |
=> a | `simple`: a `SimpleAsyncResult`.
-> Bool | `opRes`: a `Bool`.
-> m () |

Deprecated: (Since version 2.46)Use `Task` and `taskReturnBoolean` instead.

Sets the operation result to a boolean within the asynchronous result.

## setOpResGssize

simpleAsyncResultSetOpResGssize Source #

Arguments

:: (HasCallStack, MonadIO m, IsSimpleAsyncResult a) |
=> a | `simple`: a `SimpleAsyncResult`.
-> Int64 | `opRes`: a `gssize`.
-> m () |

Deprecated: (Since version 2.46)Use `Task` and `taskReturnInt` instead.

Sets the operation result within the asynchronous result to the given `opRes`.