class Gio::Task

Overview

A #GTask represents and manages a cancellable "task".

Asynchronous operations

The most common usage of #GTask is as a #GAsyncResult, to manage data during an asynchronous operation. You call g_task_new() in the "start" method, followed by g_task_set_task_data() and the like if you need to keep some additional data associated with the task, and then pass the task object around through your asynchronous operation. Eventually, you will call a method such as g_task_return_pointer() or g_task_return_error(), which will save the value you give it and then invoke the task's callback function in the [thread-default main context][g-main-context-push-thread-default] where it was created (waiting until the next iteration of the main loop first, if necessary). The caller will pass the #GTask back to the operation's finish function (as a #GAsyncResult), and you can use g_task_propagate_pointer() or the like to extract the return value.

Using #GTask requires the thread-default #GMainContext from when the #GTask was constructed to be running at least until the task has completed and its data has been freed.

Here is an example for using GTask as a GAsyncResult: |[ typedef struct { CakeFrostingType frosting; char *message; } DecorationData;

static void
decoration_data_free (DecorationData *decoration)
{
  g_free (decoration->message);
  g_slice_free (DecorationData, decoration);
}

static void
baked_cb (Cake     *cake,
          gpointer  user_data)
{
  GTask *task = user_data;
  DecorationData *decoration = g_task_get_task_data (task);
  GError *error = NULL;

  if (cake == NULL)
    {
      g_task_return_new_error (task, BAKER_ERROR, BAKER_ERROR_NO_FLOUR,
                               "Go to the supermarket");
      g_object_unref (task);
      return;
    }

  if (!cake_decorate (cake, decoration->frosting, decoration->message, &error))
    {
      g_object_unref (cake);
      // g_task_return_error() takes ownership of error
      g_task_return_error (task, error);
      g_object_unref (task);
      return;
    }

  g_task_return_pointer (task, cake, g_object_unref);
  g_object_unref (task);
}

void
baker_bake_cake_async (Baker               *self,
                       guint                radius,
                       CakeFlavor           flavor,
                       CakeFrostingType     frosting,
                       const char          *message,
                       GCancellable        *cancellable,
                       GAsyncReadyCallback  callback,
                       gpointer             user_data)
{
  GTask *task;
  DecorationData *decoration;
  Cake  *cake;

  task = g_task_new (self, cancellable, callback, user_data);
  if (radius < 3)
    {
      g_task_return_new_error (task, BAKER_ERROR, BAKER_ERROR_TOO_SMALL,
                               "%ucm radius cakes are silly",
                               radius);
      g_object_unref (task);
      return;
    }

  cake = _baker_get_cached_cake (self, radius, flavor, frosting, message);
  if (cake != NULL)
    {
      // _baker_get_cached_cake() returns a reffed cake
      g_task_return_pointer (task, cake, g_object_unref);
      g_object_unref (task);
      return;
    }

  decoration = g_slice_new (DecorationData);
  decoration->frosting = frosting;
  decoration->message = g_strdup (message);
  g_task_set_task_data (task, decoration, (GDestroyNotify) decoration_data_free);

  _baker_begin_cake (self, radius, flavor, cancellable, baked_cb, task);
}

Cake *
baker_bake_cake_finish (Baker         *self,
                        GAsyncResult  *result,
                        GError       **error)
{
  g_return_val_if_fail (g_task_is_valid (result, self), NULL);

  return g_task_propagate_pointer (G_TASK (result), error);
}

]|

Chained asynchronous operations

#GTask also tries to simplify asynchronous operations that internally chain together several smaller asynchronous operations. g_task_get_cancellable(), g_task_get_context(), and g_task_get_priority() allow you to get back the task's #GCancellable, #GMainContext, and [I/O priority][io-priority] when starting a new subtask, so you don't have to keep track of them yourself. g_task_attach_source() simplifies the case of waiting for a source to fire (automatically using the correct #GMainContext and priority).

Here is an example for chained asynchronous operations: |[ typedef struct { Cake *cake; CakeFrostingType frosting; char *message; } BakingData;

static void
decoration_data_free (BakingData *bd)
{
  if (bd->cake)
    g_object_unref (bd->cake);
  g_free (bd->message);
  g_slice_free (BakingData, bd);
}

static void
decorated_cb (Cake         *cake,
              GAsyncResult *result,
              gpointer      user_data)
{
  GTask *task = user_data;
  GError *error = NULL;

  if (!cake_decorate_finish (cake, result, &error))
    {
      g_object_unref (cake);
      g_task_return_error (task, error);
      g_object_unref (task);
      return;
    }

  // baking_data_free() will drop its ref on the cake, so we have to
  // take another here to give to the caller.
  g_task_return_pointer (task, g_object_ref (cake), g_object_unref);
  g_object_unref (task);
}

static gboolean
decorator_ready (gpointer user_data)
{
  GTask *task = user_data;
  BakingData *bd = g_task_get_task_data (task);

  cake_decorate_async (bd->cake, bd->frosting, bd->message,
                       g_task_get_cancellable (task),
                       decorated_cb, task);

  return G_SOURCE_REMOVE;
}

static void
baked_cb (Cake     *cake,
          gpointer  user_data)
{
  GTask *task = user_data;
  BakingData *bd = g_task_get_task_data (task);
  GError *error = NULL;

  if (cake == NULL)
    {
      g_task_return_new_error (task, BAKER_ERROR, BAKER_ERROR_NO_FLOUR,
                               "Go to the supermarket");
      g_object_unref (task);
      return;
    }

  bd->cake = cake;

  // Bail out now if the user has already cancelled
  if (g_task_return_error_if_cancelled (task))
    {
      g_object_unref (task);
      return;
    }

  if (cake_decorator_available (cake))
    decorator_ready (task);
  else
    {
      GSource *source;

      source = cake_decorator_wait_source_new (cake);
      // Attach *source* to *task*'s GMainContext and have it call
      // decorator_ready() when it is ready.
      g_task_attach_source (task, source, decorator_ready);
      g_source_unref (source);
    }
}

void
baker_bake_cake_async (Baker               *self,
                       guint                radius,
                       CakeFlavor           flavor,
                       CakeFrostingType     frosting,
                       const char          *message,
                       gint                 priority,
                       GCancellable        *cancellable,
                       GAsyncReadyCallback  callback,
                       gpointer             user_data)
{
  GTask *task;
  BakingData *bd;

  task = g_task_new (self, cancellable, callback, user_data);
  g_task_set_priority (task, priority);

  bd = g_slice_new0 (BakingData);
  bd->frosting = frosting;
  bd->message = g_strdup (message);
  g_task_set_task_data (task, bd, (GDestroyNotify) baking_data_free);

  _baker_begin_cake (self, radius, flavor, cancellable, baked_cb, task);
}

Cake *
baker_bake_cake_finish (Baker         *self,
                        GAsyncResult  *result,
                        GError       **error)
{
  g_return_val_if_fail (g_task_is_valid (result, self), NULL);

  return g_task_propagate_pointer (G_TASK (result), error);
}

]|

Asynchronous operations from synchronous ones

You can use g_task_run_in_thread() to turn a synchronous operation into an asynchronous one, by running it in a thread. When it completes, the result will be dispatched to the [thread-default main context][g-main-context-push-thread-default] where the #GTask was created.

Running a task in a thread: |[ typedef struct { guint radius; CakeFlavor flavor; CakeFrostingType frosting; char *message; } CakeData;

static void
cake_data_free (CakeData *cake_data)
{
  g_free (cake_data->message);
  g_slice_free (CakeData, cake_data);
}

static void
bake_cake_thread (GTask         *task,
                  gpointer       source_object,
                  gpointer       task_data,
                  GCancellable  *cancellable)
{
  Baker *self = source_object;
  CakeData *cake_data = task_data;
  Cake *cake;
  GError *error = NULL;

  cake = bake_cake (baker, cake_data->radius, cake_data->flavor,
                    cake_data->frosting, cake_data->message,
                    cancellable, &error);
  if (cake)
    g_task_return_pointer (task, cake, g_object_unref);
  else
    g_task_return_error (task, error);
}

void
baker_bake_cake_async (Baker               *self,
                       guint                radius,
                       CakeFlavor           flavor,
                       CakeFrostingType     frosting,
                       const char          *message,
                       GCancellable        *cancellable,
                       GAsyncReadyCallback  callback,
                       gpointer             user_data)
{
  CakeData *cake_data;
  GTask *task;

  cake_data = g_slice_new (CakeData);
  cake_data->radius = radius;
  cake_data->flavor = flavor;
  cake_data->frosting = frosting;
  cake_data->message = g_strdup (message);
  task = g_task_new (self, cancellable, callback, user_data);
  g_task_set_task_data (task, cake_data, (GDestroyNotify) cake_data_free);
  g_task_run_in_thread (task, bake_cake_thread);
  g_object_unref (task);
}

Cake *
baker_bake_cake_finish (Baker         *self,
                        GAsyncResult  *result,
                        GError       **error)
{
  g_return_val_if_fail (g_task_is_valid (result, self), NULL);

  return g_task_propagate_pointer (G_TASK (result), error);
}

]|

Adding cancellability to uncancellable tasks

Finally, g_task_run_in_thread() and g_task_run_in_thread_sync() can be used to turn an uncancellable operation into a cancellable one. If you call g_task_set_return_on_cancel(), passing true, then if the task's #GCancellable is cancelled, it will return control back to the caller immediately, while allowing the task thread to continue running in the background (and simply discarding its result when it finally does finish). Provided that the task thread is careful about how it uses locks and other externally-visible resources, this allows you to make "GLib-friendly" asynchronous and cancellable synchronous variants of blocking APIs.

Cancelling a task: |[ static void bake_cake_thread (GTask *task, gpointer source_object, gpointer task_data, GCancellable *cancellable) { Baker *self = source_object; CakeData *cake_data = task_data; Cake *cake; GError *error = NULL;

  cake = bake_cake (baker, cake_data->radius, cake_data->flavor,
                    cake_data->frosting, cake_data->message,
                    &error);
  if (error)
    {
      g_task_return_error (task, error);
      return;
    }

  // If the task has already been cancelled, then we don't want to add
  // the cake to the cake cache. Likewise, we don't  want to have the
  // task get cancelled in the middle of updating the cache.
  // g_task_set_return_on_cancel() will return `true` here if it managed
  // to disable return-on-cancel, or `false` if the task was cancelled
  // before it could.
  if (g_task_set_return_on_cancel (task, FALSE))
    {
      // If the caller cancels at this point, their
      // GAsyncReadyCallback won't be invoked until we return,
      // so we don't have to worry that this code will run at
      // the same time as that code does. But if there were
      // other functions that might look at the cake cache,
      // then we'd probably need a GMutex here as well.
      baker_add_cake_to_cache (baker, cake);
      g_task_return_pointer (task, cake, g_object_unref);
    }
}

void
baker_bake_cake_async (Baker               *self,
                       guint                radius,
                       CakeFlavor           flavor,
                       CakeFrostingType     frosting,
                       const char          *message,
                       GCancellable        *cancellable,
                       GAsyncReadyCallback  callback,
                       gpointer             user_data)
{
  CakeData *cake_data;
  GTask *task;

  cake_data = g_slice_new (CakeData);

  ...

  task = g_task_new (self, cancellable, callback, user_data);
  g_task_set_task_data (task, cake_data, (GDestroyNotify) cake_data_free);
  g_task_set_return_on_cancel (task, TRUE);
  g_task_run_in_thread (task, bake_cake_thread);
}

Cake *
baker_bake_cake_sync (Baker               *self,
                      guint                radius,
                      CakeFlavor           flavor,
                      CakeFrostingType     frosting,
                      const char          *message,
                      GCancellable        *cancellable,
                      GError             **error)
{
  CakeData *cake_data;
  GTask *task;
  Cake *cake;

  cake_data = g_slice_new (CakeData);

  ...

  task = g_task_new (self, cancellable, NULL, NULL);
  g_task_set_task_data (task, cake_data, (GDestroyNotify) cake_data_free);
  g_task_set_return_on_cancel (task, TRUE);
  g_task_run_in_thread_sync (task, bake_cake_thread);

  cake = g_task_propagate_pointer (task, error);
  g_object_unref (task);
  return cake;
}

]|

Porting from GSimpleAsyncResult

#GTask's API attempts to be simpler than #GSimpleAsyncResult's in several ways:

Included Modules

Defined in:

lib/gi-crystal/src/auto/gio-2.0/task.cr

Constructors

Class Method Summary

Instance Method Summary

Instance methods inherited from module Gio::AsyncResult

is_tagged(source_tag : Pointer(Void) | Nil) : Bool is_tagged, legacy_propagate_error : Bool legacy_propagate_error, source_object : GObject::Object | Nil source_object, to_unsafe to_unsafe, user_data : Pointer(Void) | Nil user_data

Constructor methods inherited from module Gio::AsyncResult

cast(obj : GObject::Object) : self cast

Class methods inherited from module Gio::AsyncResult

cast?(obj : GObject::Object) : self | Nil cast?, g_type : UInt64 g_type

Instance methods inherited from class GObject::Object

==(other : self) ==, bind_property(source_property : String, target : GObject::Object, target_property : String, flags : GObject::BindingFlags) : GObject::Binding bind_property, bind_property_full(source_property : String, target : GObject::Object, target_property : String, flags : GObject::BindingFlags, transform_to : GObject::Closure, transform_from : GObject::Closure) : GObject::Binding bind_property_full, data(key : String) : Pointer(Void) | Nil data, finalize finalize, freeze_notify : Nil freeze_notify, getv(names : Enumerable(String), values : Enumerable(_)) : Nil getv, hash(hasher) hash, notify(property_name : String) : Nil notify, notify_by_pspec(pspec : GObject::ParamSpec) : Nil notify_by_pspec, notify_signal notify_signal, property(property_name : String, value : _) : Nil property, qdata(quark : UInt32) : Pointer(Void) | Nil qdata, ref_count : UInt32 ref_count, run_dispose : Nil run_dispose, set_data(key : String, data : Pointer(Void) | Nil) : Nil set_data, set_property(property_name : String, value : _) : Nil set_property, steal_data(key : String) : Pointer(Void) | Nil steal_data, steal_qdata(quark : UInt32) : Pointer(Void) | Nil steal_qdata, thaw_notify : Nil thaw_notify, to_unsafe : Pointer(Void) to_unsafe, watch_closure(closure : GObject::Closure) : Nil watch_closure

Constructor methods inherited from class GObject::Object

cast(obj : GObject::Object) : self cast, new(pointer : Pointer(Void), transfer : GICrystal::Transfer)
new
new
, newv(object_type : UInt64, parameters : Enumerable(GObject::Parameter)) : self newv

Class methods inherited from class GObject::Object

cast?(obj : GObject::Object) : self | Nil cast?, compat_control(what : UInt64, data : Pointer(Void) | Nil) : UInt64 compat_control, g_type : UInt64 g_type, interface_find_property(g_iface : GObject::TypeInterface, property_name : String) : GObject::ParamSpec interface_find_property, interface_list_properties(g_iface : GObject::TypeInterface) : Enumerable(GObject::ParamSpec) interface_list_properties

Constructor Detail

def self.new(source_object : GObject::Object | Nil, cancellable : Gio::Cancellable | Nil, callback : Gio::AsyncReadyCallback | Nil, callback_data : Pointer(Void) | Nil) : self #

Creates a #GTask acting on source_object, which will eventually be used to invoke callback in the current [thread-default main context][g-main-context-push-thread-default].

Call this in the "start" method of your asynchronous method, and pass the #GTask around throughout the asynchronous operation. You can use g_task_set_task_data() to attach task-specific data to the object, which you can retrieve later via g_task_get_task_data().

By default, if cancellable is cancelled, then the return value of the task will always be %G_IO_ERROR_CANCELLED, even if the task had already completed before the cancellation. This allows for simplified handling in cases where cancellation may imply that other objects that the task depends on have been destroyed. If you do not want this behavior, you can use g_task_set_check_cancellable() to change it.


[View source]
def self.new #

Initialize a new Task.


[View source]
def self.new(*, completed : Bool | Nil = nil) #

[View source]

Class Method Detail

def self.g_type : UInt64 #

Returns the type id (GType) registered in GLib type system.


[View source]
def self.is_valid(result : Gio::AsyncResult, source_object : GObject::Object | Nil) : Bool #

Checks that result is a #GTask, and that source_object is its source object (or that source_object is nil and result has no source object). This can be used in g_return_if_fail() checks.


[View source]
def self.report_error(source_object : GObject::Object | Nil, callback : Gio::AsyncReadyCallback | Nil, callback_data : Pointer(Void) | Nil, source_tag : Pointer(Void) | Nil, error : GLib::Error) : Nil #

Creates a #GTask and then immediately calls g_task_return_error() on it. Use this in the wrapper function of an asynchronous method when you want to avoid even calling the virtual method. You can then use g_async_result_is_tagged() in the finish method wrapper to check if the result there is tagged as having been created by the wrapper method, and deal with it appropriately if so.

See also g_task_report_new_error().


[View source]

Instance Method Detail

def ==(other : self) #
Description copied from class Reference

Returns true if this reference is the same as other. Invokes same?.


def cancellable : Gio::Cancellable #

Gets task's #GCancellable


[View source]
def check_cancellable : Bool #

Gets task's check-cancellable flag. See g_task_set_check_cancellable() for more details.


[View source]
def check_cancellable=(check_cancellable : Bool) : Nil #

Sets or clears task's check-cancellable flag. If this is true (the default), then g_task_propagate_pointer(), etc, and g_task_had_error() will check the task's #GCancellable first, and if it has been cancelled, then they will consider the task to have returned an "Operation was cancelled" error (%G_IO_ERROR_CANCELLED), regardless of any other error or return value the task may have had.

If check_cancellable is false, then the #GTask will not check the cancellable itself, and it is up to task's owner to do this (eg, via g_task_return_error_if_cancelled()).

If you are using g_task_set_return_on_cancel() as well, then you must leave check-cancellable set true.


[View source]
def completed : Bool #

Gets the value of #GTask:completed. This changes from false to true after the task’s callback is invoked, and will return false if called from inside the callback.


[View source]
def completed? : Bool #

[View source]
def context : GLib::MainContext #

Gets the #GMainContext that task will return its result in (that is, the context that was the [thread-default main context][g-main-context-push-thread-default] at the point when task was created).

This will always return a non-nil value, even if the task's context is the default #GMainContext.


[View source]
def had_error : Bool #

Tests if task resulted in an error.


[View source]
def hash(hasher) #
Description copied from class Reference

See Object#hash(hasher)


def name : String | Nil #

Gets task’s name. See g_task_set_name().


[View source]
def name=(name : String | Nil) : Nil #

Sets task’s name, used in debugging and profiling. The name defaults to nil.

The task name should describe in a human readable way what the task does. For example, ‘Open file’ or ‘Connect to network host’. It is used to set the name of the #GSource used for idle completion of the task.

This function may only be called before the task is first used in a thread other than the one it was constructed in. It is called automatically by g_task_set_source_tag() if not called already.


[View source]
def priority : Int32 #

Gets task's priority


[View source]
def priority=(priority : Int32) : Nil #

Sets task's priority. If you do not call this, it will default to %G_PRIORITY_DEFAULT.

This will affect the priority of #GSources created with g_task_attach_source() and the scheduling of tasks run in threads, and can also be explicitly retrieved later via g_task_get_priority().


[View source]
def propagate_boolean : Bool #

Gets the result of task as a #gboolean.

If the task resulted in an error, or was cancelled, then this will instead return false and set error.

Since this method transfers ownership of the return value (or error) to the caller, you may only call it once.


[View source]
def propagate_int : Int64 #

Gets the result of task as an integer (#gssize).

If the task resulted in an error, or was cancelled, then this will instead return -1 and set error.

Since this method transfers ownership of the return value (or error) to the caller, you may only call it once.


[View source]
def propagate_pointer : Pointer(Void) | Nil #

Gets the result of task as a pointer, and transfers ownership of that value to the caller.

If the task resulted in an error, or was cancelled, then this will instead return nil and set error.

Since this method transfers ownership of the return value (or error) to the caller, you may only call it once.


[View source]
def propagate_value : GObject::Value #

Gets the result of task as a #GValue, and transfers ownership of that value to the caller. As with g_task_return_value(), this is a generic low-level method; g_task_propagate_pointer() and the like will usually be more useful for C code.

If the task resulted in an error, or was cancelled, then this will instead set error and return false.

Since this method transfers ownership of the return value (or error) to the caller, you may only call it once.


[View source]
def return_boolean(result : Bool) : Nil #

Sets task's result to result and completes the task (see g_task_return_pointer() for more discussion of exactly what this means).


[View source]
def return_error(error : GLib::Error) : Nil #

Sets task's result to error (which task assumes ownership of) and completes the task (see g_task_return_pointer() for more discussion of exactly what this means).

Note that since the task takes ownership of error, and since the task may be completed before returning from g_task_return_error(), you cannot assume that error is still valid after calling this. Call g_error_copy() on the error if you need to keep a local copy as well.

See also g_task_return_new_error().


[View source]
def return_error_if_cancelled : Bool #

Checks if task's #GCancellable has been cancelled, and if so, sets task's error accordingly and completes the task (see g_task_return_pointer() for more discussion of exactly what this means).


[View source]
def return_int(result : Int64) : Nil #

Sets task's result to result and completes the task (see g_task_return_pointer() for more discussion of exactly what this means).


[View source]
def return_on_cancel : Bool #

Gets task's return-on-cancel flag. See g_task_set_return_on_cancel() for more details.


[View source]
def return_on_cancel=(return_on_cancel : Bool) : Bool #

Sets or clears task's return-on-cancel flag. This is only meaningful for tasks run via g_task_run_in_thread() or g_task_run_in_thread_sync().

If return_on_cancel is true, then cancelling task's #GCancellable will immediately cause it to return, as though the task's #GTaskThreadFunc had called g_task_return_error_if_cancelled() and then returned.

This allows you to create a cancellable wrapper around an uninterruptible function. The #GTaskThreadFunc just needs to be careful that it does not modify any externally-visible state after it has been cancelled. To do that, the thread should call g_task_set_return_on_cancel() again to (atomically) set return-on-cancel false before making externally-visible changes; if the task gets cancelled before the return-on-cancel flag could be changed, g_task_set_return_on_cancel() will indicate this by returning false.

You can disable and re-enable this flag multiple times if you wish. If the task's #GCancellable is cancelled while return-on-cancel is false, then calling g_task_set_return_on_cancel() to set it true again will cause the task to be cancelled at that point.

If the task's #GCancellable is already cancelled before you call g_task_run_in_thread()/g_task_run_in_thread_sync(), then the #GTaskThreadFunc will still be run (for consistency), but the task will also be completed right away.


[View source]
def return_pointer(result : Pointer(Void) | Nil, result_destroy : GLib::DestroyNotify | Nil) : Nil #

Sets task's result to result and completes the task. If result is not nil, then result_destroy will be used to free result if the caller does not take ownership of it with g_task_propagate_pointer().

"Completes the task" means that for an ordinary asynchronous task it will either invoke the task's callback, or else queue that callback to be invoked in the proper #GMainContext, or in the next iteration of the current #GMainContext. For a task run via g_task_run_in_thread() or g_task_run_in_thread_sync(), calling this method will save result to be returned to the caller later, but the task will not actually be completed until the #GTaskThreadFunc exits.

Note that since the task may be completed before returning from g_task_return_pointer(), you cannot assume that result is still valid after calling this, unless you are still holding another reference on it.


[View source]
def return_value(result : _ | Nil) : Nil #

Sets task's result to result (by copying it) and completes the task.

If result is nil then a #GValue of type %G_TYPE_POINTER with a value of nil will be used for the result.

This is a very generic low-level method intended primarily for use by language bindings; for C code, g_task_return_pointer() and the like will normally be much easier to use.


[View source]
def run_in_thread(task_func : Gio::TaskThreadFunc) : Nil #

Runs task_func in another thread. When task_func returns, task's #GAsyncReadyCallback will be invoked in task's #GMainContext.

This takes a ref on task until the task completes.

See #GTaskThreadFunc for more details about how task_func is handled.

Although GLib currently rate-limits the tasks queued via g_task_run_in_thread(), you should not assume that it will always do this. If you have a very large number of tasks to run (several tens of tasks), but don't want them to all run at once, you should only queue a limited number of them (around ten) at a time.


[View source]
def run_in_thread_sync(task_func : Gio::TaskThreadFunc) : Nil #

Runs task_func in another thread, and waits for it to return or be cancelled. You can use g_task_propagate_pointer(), etc, afterward to get the result of task_func.

See #GTaskThreadFunc for more details about how task_func is handled.

Normally this is used with tasks created with a nil callback, but note that even if the task does have a callback, it will not be invoked when task_func returns. #GTask:completed will be set to true just before this function returns.

Although GLib currently rate-limits the tasks queued via g_task_run_in_thread_sync(), you should not assume that it will always do this. If you have a very large number of tasks to run, but don't want them to all run at once, you should only queue a limited number of them at a time.


[View source]
def set_task_data(task_data : Pointer(Void) | Nil, task_data_destroy : GLib::DestroyNotify | Nil) : Nil #

Sets task's task data (freeing the existing task data, if any).


[View source]
def source_object : GObject::Object | Nil #

Gets the source object from task. Like g_async_result_get_source_object(), but does not ref the object.


[View source]
def source_tag : Pointer(Void) | Nil #

Gets task's source tag. See g_task_set_source_tag().


[View source]
def source_tag=(source_tag : Pointer(Void) | Nil) : Nil #

Sets task's source tag.

You can use this to tag a task return value with a particular pointer (usually a pointer to the function doing the tagging) and then later check it using g_task_get_source_tag() (or g_async_result_is_tagged()) in the task's "finish" function, to figure out if the response came from a particular place.

A macro wrapper around this function will automatically set the task’s name to the string form of source_tag if it’s not already set, for convenience.


[View source]
def task_data : Pointer(Void) | Nil #

Gets task's #task_data.


[View source]