BindingProtocol

public protocol BindingProtocol : ObjectProtocol

The BindingProtocol protocol exposes the methods and properties of an underlying GBinding instance. The default implementation of these can be found in the protocol extension below. For a concrete class that implements these methods and properties, see Binding. Alternatively, use BindingRef as a lighweight, unowned reference if you already have an instance you just want to use.

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:

(C Language Example):

  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:

(C Language Example):

  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:

(C Language Example):

  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

  • ptr

    Untyped pointer to the underlying GBinding instance.

    Declaration

    Swift

    var ptr: UnsafeMutableRawPointer { get }
  • binding_ptr Default implementation

    Typed pointer to the underlying GBinding instance.

    Default Implementation

    Return the stored, untyped pointer as a typed pointer to the GBinding instance.

    Declaration

    Swift

    var binding_ptr: UnsafeMutablePointer<GBinding> { get }

Binding Class

Binding Class: BindingProtocol extension (methods and fields)

  • getFlags() Extension method

    Retrieves the flags passed when constructing the GBinding.

    Declaration

    Swift

    func getFlags() -> GBindingFlags
  • getSource() Extension method

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

    Declaration

    Swift

    func getSource() -> UnsafeMutablePointer<GObject>!
  • getSourceProperty() Extension method

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

    Declaration

    Swift

    func getSourceProperty() -> String!
  • getTarget() Extension method

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

    Declaration

    Swift

    func getTarget() -> UnsafeMutablePointer<GObject>!
  • getTargetProperty() Extension method

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

    Declaration

    Swift

    func getTargetProperty() -> String!
  • unbind() Extension method

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

    This function will release the reference that is being held on the binding instance; if you want to hold on to the GBinding instance after calling g_binding_unbind(), you will need to hold a reference to it.

    Declaration

    Swift

    func unbind()
  • flags Extension method

    Flags to be used to control the GBinding

    Declaration

    Swift

    var flags: GBindingFlags { get }
  • source Extension method

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

    Declaration

    Swift

    var source: UnsafeMutablePointer<GObject>! { get }
  • sourceProperty Extension method

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

    Declaration

    Swift

    var sourceProperty: String! { get }
  • target Extension method

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

    Declaration

    Swift

    var target: UnsafeMutablePointer<GObject>! { get }
  • targetProperty Extension method

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

    Declaration

    Swift

    var targetProperty: String! { get }