BindingRef
public struct BindingRef : BindingProtocol, GWeakCapturing
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
The BindingRef
type acts as a lightweight Swift reference to an underlying GBinding
instance.
It exposes methods that can operate on this data type through BindingProtocol
conformance.
Use BindingRef
only as an unowned
reference to an existing GBinding
instance.
-
Untyped pointer to the underlying `GBinding` instance.
For type-safe access, use the generated, typed pointer
binding_ptr
property instead.Declaration
Swift
public let ptr: UnsafeMutableRawPointer!
-
Designated initialiser from the underlying
C
data typeDeclaration
Swift
@inlinable init(_ p: UnsafeMutablePointer<GBinding>)
-
Designated initialiser from a constant pointer to the underlying
C
data typeDeclaration
Swift
@inlinable init(_ p: UnsafePointer<GBinding>)
-
Conditional initialiser from an optional pointer to the underlying
C
data typeDeclaration
Swift
@inlinable init!(_ maybePointer: UnsafeMutablePointer<GBinding>?)
-
Conditional initialiser from an optional, non-mutable pointer to the underlying
C
data typeDeclaration
Swift
@inlinable init!(_ maybePointer: UnsafePointer<GBinding>?)
-
Conditional initialiser from an optional
gpointer
Declaration
Swift
@inlinable init!(gpointer g: gpointer?)
-
Conditional initialiser from an optional, non-mutable
gconstpointer
Declaration
Swift
@inlinable init!(gconstpointer g: gconstpointer?)
-
Reference intialiser for a related type that implements
BindingProtocol
Declaration
Swift
@inlinable init<T>(_ other: T) where T : BindingProtocol
-
This factory is syntactic sugar for setting weak pointers wrapped in
GWeak<T>
Declaration
Swift
@inlinable static func unowned<T>(_ other: T) -> BindingRef where T : BindingProtocol
-
Unsafe typed initialiser. Do not use unless you know the underlying data type the pointer points to conforms to
BindingProtocol
.Declaration
Swift
@inlinable init<T>(cPointer: UnsafeMutablePointer<T>)
-
Unsafe typed initialiser. Do not use unless you know the underlying data type the pointer points to conforms to
BindingProtocol
.Declaration
Swift
@inlinable init<T>(constPointer: UnsafePointer<T>)
-
Unsafe untyped initialiser. Do not use unless you know the underlying data type the pointer points to conforms to
BindingProtocol
.Declaration
Swift
@inlinable init(mutating raw: UnsafeRawPointer)
-
Unsafe untyped initialiser. Do not use unless you know the underlying data type the pointer points to conforms to
BindingProtocol
.Declaration
Swift
@inlinable init(raw: UnsafeMutableRawPointer)
-
Unsafe untyped initialiser. Do not use unless you know the underlying data type the pointer points to conforms to
BindingProtocol
.Declaration
Swift
@inlinable init(opaquePointer: OpaquePointer)