Class

GObjectBinding

Description

final class GObject.Binding : GObject.Object {
  /* No available fields */
}

GBinding is the representation of a binding between a property on a GObject instance (or source) and another property on another GObject instance (or target).

Whenever the source property changes, the same value is applied to the target property; for instance, the following binding:

  g_object_bind_property (object1, "property-a",
                          object2, "property-b",
                          G_BINDING_DEFAULT);

will cause the property named “property-b” of object2 to be updated every time g_object_set() or the specific accessor changes the value of the property “property-a” of object1.

It is possible to create a bidirectional binding between two properties of two GObject instances, so that if either property changes, the other is updated as well, for instance:

  g_object_bind_property (object1, "property-a",
                          object2, "property-b",
                          G_BINDING_BIDIRECTIONAL);

will keep the two properties in sync.

It is also possible to set a custom transformation function (in both directions, in case of a bidirectional binding) to apply a custom transformation from the source value to the target value before applying it; for instance, the following binding:

  g_object_bind_property_full (adjustment1, "value",
                               adjustment2, "value",
                               G_BINDING_BIDIRECTIONAL,
                               celsius_to_fahrenheit,
                               fahrenheit_to_celsius,
                               NULL, NULL);

will keep the “value” property of the two adjustments in sync; the celsius_to_fahrenheit function will be called whenever the “value” property of adjustment1 changes and will transform the current value of the property before applying it to the “value” property of adjustment2.

Vice versa, the fahrenheit_to_celsius function will be called whenever the “value” property of adjustment2 changes, and will transform the current value of the property before applying it to the “value” property of adjustment1.

Note that GBinding does not resolve cycles by itself; a cycle like

  object1:propertyA -> object2:propertyB
  object2:propertyB -> object3:propertyC
  object3:propertyC -> object1:propertyA

might lead to an infinite loop. The loop, in this particular case, can be avoided if the objects emit the GObject::notify signal only if the value has effectively been changed. A binding is implemented using the GObject::notify signal, so it is susceptible to all the various ways of blocking a signal emission, like g_signal_stop_emission() or g_signal_handler_block().

A binding will be severed, and the resources it allocates freed, whenever either one of the GObject instances it refers to are finalized, or when the GBinding instance loses its last reference.

Bindings for languages with garbage collection can use g_binding_unbind() to explicitly release a binding between the source and target properties, instead of relying on the last reference on the binding, source, and target instances to drop.

GBinding is available since GObject 2.26

Available since:2.26

Hierarchy

hierarchy this GBinding ancestor_0 GObject ancestor_0--this

Ancestors

Instance methods

g_binding_dup_source

Retrieves the GObject instance used as the source of the binding.

Available since: 2.68

g_binding_dup_target

Retrieves the GObject instance used as the target of the binding.

Available since: 2.68

g_binding_get_flags

Retrieves the flags passed when constructing the GBinding.

Available since: 2.26

g_binding_get_source

Retrieves the GObject instance used as the source of the binding.

Available since: 2.26

Deprecated since: 2.68

g_binding_get_source_property

Retrieves the name of the property of GBinding:source used as the source of the binding.

Available since: 2.26

g_binding_get_target

Retrieves the GObject instance used as the target of the binding.

Available since: 2.26

Deprecated since: 2.68

g_binding_get_target_property

Retrieves the name of the property of GBinding:target used as the target of the binding.

Available since: 2.26

g_binding_unbind

Explicitly releases the binding between the source and the target property expressed by binding.

Available since: 2.38

Methods inherited from GObject (43)

Please see GObject for a full list of methods.

Properties

GObject.Binding:flags

Flags to be used to control the GBinding.

Available since: 2.26

GObject.Binding:source

The GObject that should be used as the source of the binding.

Available since: 2.26

GObject.Binding:source-property

The name of the property of GBinding:source that should be used as the source of the binding.

Available since: 2.26

GObject.Binding:target

The GObject that should be used as the target of the binding.

Available since: 2.26

GObject.Binding:target-property

The name of the property of GBinding:target that should be used as the target of the binding.

Available since: 2.26

Signals

Signals inherited from GObject (1)
GObject.Object::notify

The notify signal is emitted on an object when one of its properties has its value set through g_object_set_property(), g_object_set(), et al.