Class Service

Whenever the source_property is changed the target_property is updated using the same value. For instance:

  g_object_bind_property (action, "active", widget, "sensitive", 0);

Will result in the "sensitive" property of the widget #GObject instance to be updated with the same value of the "active" property of the action #GObject instance.

If flags contains %G_BINDING_BIDIRECTIONAL then the binding will be mutual: if target_property on target changes then the source_property on source will be updated as well.

The binding will automatically be removed when either the source or the target instances are finalized. To remove the binding without affecting the source and the target you can just call g_object_unref() on the returned #GBinding instance.

Removing the binding by calling g_object_unref() on it must only be done if the binding, source and target are only used from a single thread and it is clear that both source and target outlive the binding. Especially it is not safe to rely on this if the binding, source or target can be finalized from different threads. Keep another reference to the binding and use g_binding_unbind() instead to be on the safe side.

A #GObject can have multiple bindings.

This function is the language bindings friendly version of g_object_bind_property_full(), using #GClosures instead of function pointers.

If method_name contains any dots, then name is split into interface and method name parts. This allows using proxy for invoking methods on other interfaces.

If the #GDBusConnection associated with proxy is closed then the operation will fail with %G_IO_ERROR_CLOSED. If cancellable is canceled, the operation will fail with %G_IO_ERROR_CANCELLED. If parameters contains a value not compatible with the D-Bus protocol, the operation fails with %G_IO_ERROR_INVALID_ARGUMENT.

If the parameters #GVariant is floating, it is consumed. This allows convenient 'inline' use of g_variant_new(), e.g.:

 g_dbus_proxy_call (proxy,
                    "TwoStrings",
                    g_variant_new ("(ss)",
                                   "Thing One",
                                   "Thing Two"),
                    G_DBUS_CALL_FLAGS_NONE,
                    -1,
                    NULL,
                    (GAsyncReadyCallback) two_strings_done,
                    &data);

If proxy has an expected interface (see #GDBusProxy:g-interface-info) and method_name is referenced by it, then the return value is checked against the return type.

This is an asynchronous method. When the operation is finished, callback will be invoked in the [thread-default main context][g-main-context-push-thread-default] of the thread you are calling this method from. You can then call g_dbus_proxy_call_finish() to get the result of the operation. See g_dbus_proxy_call_sync() for the synchronous version of this method.

If callback is %NULL then the D-Bus method call message will be sent with the %G_DBUS_MESSAGE_FLAGS_NO_REPLY_EXPECTED flag set.

If method_name contains any dots, then name is split into interface and method name parts. This allows using proxy for invoking methods on other interfaces.

If the #GDBusConnection associated with proxy is disconnected then the operation will fail with %G_IO_ERROR_CLOSED. If cancellable is canceled, the operation will fail with %G_IO_ERROR_CANCELLED. If parameters contains a value not compatible with the D-Bus protocol, the operation fails with %G_IO_ERROR_INVALID_ARGUMENT.

If the parameters #GVariant is floating, it is consumed. This allows convenient 'inline' use of g_variant_new(), e.g.:

 g_dbus_proxy_call_sync (proxy,
                         "TwoStrings",
                         g_variant_new ("(ss)",
                                        "Thing One",
                                        "Thing Two"),
                         G_DBUS_CALL_FLAGS_NONE,
                         -1,
                         NULL,
                         &error);

The calling thread is blocked until a reply is received. See g_dbus_proxy_call() for the asynchronous version of this method.

If proxy has an expected interface (see #GDBusProxy:g-interface-info) and method_name is referenced by it, then the return value is checked against the return type.

This method is only available on UNIX.

This method is only available on UNIX.

This is necessary for accessors that modify multiple properties to prevent premature notification while the object is still being modified.

If proxy has an expected interface (see #GDBusProxy:g-interface-info) and property_name is referenced by it, then value is checked against the type of the property.

See the #GDBusProxy:g-default-timeout property for more details.

Use [methodService.ensure_session] or [methodService.load_collections] to initialize further features and change the flags.

When connected to a message bus, this will usually be non-%NULL. However, it may be %NULL for a proxy that communicates using a peer-to-peer pattern.

The value can be:

• an empty #GValue initialized by %G_VALUE_INIT, which will be automatically initialized with the expected type of the property (since GLib 2.60)
• a #GValue initialized with the expected type of the property
• a #GValue initialized with a type to which the expected type of the property can be transformed

In general, a copy is made of the property contents and the caller is responsible for freeing the memory by calling g_value_unset().

Note that g_object_get_property() is really intended for language bindings, g_object_get() is much more convenient for C programming.

This method is intended for language bindings. If writing in C, g_initable_new() should typically be used instead.

The object must be initialized before any real use after initial construction, either with this function or g_async_initable_init_async().

Implementations may also support cancellation. If cancellable is not %NULL, then initialization can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error %G_IO_ERROR_CANCELLED will be returned. If cancellable is not %NULL and the object doesn't support cancellable initialization the error %G_IO_ERROR_NOT_SUPPORTED will be returned.

If the object is not initialized, or initialization returns with an error, then all operations on the object except g_object_ref() and g_object_unref() are considered to be invalid, and have undefined behaviour. See the [introduction][ginitable] for more details.

Callers should not assume that a class which implements #GInitable can be initialized multiple times, unless the class explicitly documents itself as supporting this. Generally, a class’ implementation of init() can assume (and assert) that it will only be called once. Previously, this documentation recommended all #GInitable implementations should be idempotent; that recommendation was relaxed in GLib 2.54.

If a class explicitly supports being initialized multiple times, it is recommended that the method is idempotent: multiple calls with the same arguments should return the same results. Only the first call initializes the object; further calls return the result of the first call.

One reason why a class might need to support idempotent initialization is if it is designed to be used via the singleton pattern, with a #GObjectClass.constructor that sometimes returns an existing instance. In this pattern, a caller would expect to be able to call g_initable_init() on the result of g_object_new(), regardless of whether it is in fact a new instance.

This method is intended for language bindings. If writing in C, g_async_initable_new_async() should typically be used instead.

When the initialization is finished, callback will be called. You can then call g_async_initable_init_finish() to get the result of the initialization.

Implementations may also support cancellation. If cancellable is not %NULL, then initialization can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error %G_IO_ERROR_CANCELLED will be returned. If cancellable is not %NULL, and the object doesn't support cancellable initialization, the error %G_IO_ERROR_NOT_SUPPORTED will be returned.

As with #GInitable, if the object is not initialized, or initialization returns with an error, then all operations on the object except g_object_ref() and g_object_unref() are considered to be invalid, and have undefined behaviour. They will often fail with g_critical() or g_warning(), but this must not be relied on.

Callers should not assume that a class which implements #GAsyncInitable can be initialized multiple times; for more information, see g_initable_init(). If a class explicitly supports being initialized multiple times, implementation requires yielding all subsequent calls to init_async() on the results of the first call.

For classes that also support the #GInitable interface, the default implementation of this method will run the g_initable_init() function in a thread, so if you want to support asynchronous initialization via threads, just implement the #GAsyncInitable interface without overriding any interface methods.

When possible, eg. when signaling a property change from within the class that registered the property, you should use g_object_notify_by_pspec() instead.

Note that emission of the notify signal may be blocked with g_object_freeze_notify(). In this case, the signal emissions are queued and will be emitted (in reverse order) when g_object_thaw_notify() is called.

This function omits the property name lookup, hence it is faster than g_object_notify().

One way to avoid using g_object_notify() from within the class that registered the properties, and using g_object_notify_by_pspec() instead, is to store the GParamSpec used with g_object_class_install_property() inside a static array, e.g.:

  enum
  {
    PROP_0,
    PROP_FOO,
    PROP_LAST
  };

  static GParamSpec *properties[PROP_LAST];

  static void
  my_object_class_init (MyObjectClass *klass)
  {
    properties[PROP_FOO] = g_param_spec_int ("foo", "Foo", "The foo",
                                             0, 100,
                                             50,
                                             G_PARAM_READWRITE);
    g_object_class_install_property (gobject_class,
                                     PROP_FOO,
                                     properties[PROP_FOO]);
  }

and then notify a change on the "foo" property with:

  g_object_notify_by_pspec (self, properties[PROP_FOO]);

Since GLib 2.56, if GLIB_VERSION_MAX_ALLOWED is 2.56 or greater, the type of object will be propagated to the return type (using the GCC typeof() extension), so any casting the caller needs to do on the return type must be explicit.

In other words, if the object is floating, then this call "assumes ownership" of the floating reference, converting it to a normal reference by clearing the floating flag while leaving the reference count unchanged. If the object is not floating, then this call adds a new normal reference increasing the reference count by one.

Since GLib 2.56, the type of object will be propagated to the return type under the same conditions as for g_object_ref().

This function should only be called from object system implementations.

If value is %NULL, then the cached value is removed from the property cache.

If proxy has an expected interface (see #GDBusProxy:g-interface-info) and property_name is referenced by it, then value is checked against the type of the property.

If the value #GVariant is floating, it is consumed. This allows convenient 'inline' use of g_variant_new(), e.g.

 g_dbus_proxy_set_cached_property (proxy,
                                   "SomeProperty",
                                   g_variant_new ("(si)",
                                                 "A String",
                                                 42));

Normally you will not need to use this method since proxy is tracking changes using the org.freedesktop.DBus.Properties.PropertiesChanged D-Bus signal. However, for performance reasons an object may decide to not use this signal for some properties and instead use a proprietary out-of-band mechanism to transmit changes.

As a concrete example, consider an object with a property ChatroomParticipants which is an array of strings. Instead of transmitting the same (long) array every time the property changes, it is more efficient to only transmit the delta using e.g. signals ChatroomParticipantJoined(String name) and ChatroomParticipantParted(String name).

If the object already had an association with that name, the old association will be destroyed.

Internally, the key is converted to a #GQuark using g_quark_from_string(). This means a copy of key is kept permanently (even after object has been finalized) — so it is recommended to only use a small, bounded set of values for key in your program, to avoid the #GQuark storage growing unbounded.

See the #GDBusProxy:g-default-timeout property for more details.