GObject.Binding

g GObject.Binding GObject.Binding GObject.Object GObject.Object GObject.Object->GObject.Binding

Subclasses

None

Methods

Inherited

GObject.Object (37)

Structs

GObject.ObjectClass (5)

dup_source ()

dup_target ()

get_flags ()

get_source ()

get_source_property ()

get_target ()

get_target_property ()

unbind ()

Virtual Methods

Inherited

GObject.Object (7)

Properties

Name

Type

Flags

Short Description

flags

GObject.BindingFlags

r/w/co

The binding flags

source

GObject.Object

r/w/co

The source of the binding

source-property

str

r/w/co

The property on the source to bind

target

GObject.Object

r/w/co

The target of the binding

target-property

str

r/w/co

The property on the target to bind

Signals

Inherited

GObject.Object (1)

Fields

Inherited

GObject.Object (1)

Class Details

class GObject.Binding(**kwargs)
Bases

GObject.Object

Abstract

No

GObject.Binding is the representation of a binding between a property on a GObject.Object instance (or source) and another property on another GObject.Object 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.Object 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 GObject.Binding 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.Object ::notify signal only if the value has effectively been changed. A binding is implemented using the GObject.Object ::notify signal, so it is susceptible to all the various ways of blocking a signal emission, like GObject.signal_stop_emission() or GObject.signal_handler_block().

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

Bindings for languages with garbage collection can use GObject.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.

GObject.Binding is available since GObject.Object 2.26

New in version 2.26.

dup_source()
Returns

the source GObject.Object, or None if the source does not exist any more.

Return type

GObject.Object or None

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

A GObject.Binding can outlive the source GObject.Object as the binding does not hold a strong reference to the source. If the source is destroyed before the binding then this function will return None.

New in version 2.68.

dup_target()
Returns

the target GObject.Object, or None if the target does not exist any more.

Return type

GObject.Object or None

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

A GObject.Binding can outlive the target GObject.Object as the binding does not hold a strong reference to the target. If the target is destroyed before the binding then this function will return None.

New in version 2.68.

get_flags()
Returns

the GObject.BindingFlags used by the GObject.Binding

Return type

GObject.BindingFlags

Retrieves the flags passed when constructing the GObject.Binding.

New in version 2.26.

get_source()
Returns

the source GObject.Object, or None if the source does not exist any more.

Return type

GObject.Object or None

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

A GObject.Binding can outlive the source GObject.Object as the binding does not hold a strong reference to the source. If the source is destroyed before the binding then this function will return None.

Use GObject.Binding.dup_source() if the source or binding are used from different threads as otherwise the pointer returned from this function might become invalid if the source is finalized from another thread in the meantime.

New in version 2.26.

Deprecated since version 2.68: Use GObject.Binding.dup_source() for a safer version of this function.

get_source_property()
Returns

the name of the source property

Return type

str

Retrieves the name of the property of GObject.Binding :source used as the source of the binding.

New in version 2.26.

get_target()
Returns

the target GObject.Object, or None if the target does not exist any more.

Return type

GObject.Object or None

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

A GObject.Binding can outlive the target GObject.Object as the binding does not hold a strong reference to the target. If the target is destroyed before the binding then this function will return None.

Use GObject.Binding.dup_target() if the target or binding are used from different threads as otherwise the pointer returned from this function might become invalid if the target is finalized from another thread in the meantime.

New in version 2.26.

Deprecated since version 2.68: Use GObject.Binding.dup_target() for a safer version of this function.

get_target_property()
Returns

the name of the target property

Return type

str

Retrieves the name of the property of GObject.Binding :target used as the target of the binding.

New in version 2.26.

unbind()

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

This function will release the reference that is being held on the self instance if the binding is still bound; if you want to hold on to the GObject.Binding instance after calling GObject.Binding.unbind(), you will need to hold a reference to it.

Note however that this function does not take ownership of self, it only unrefs the reference that was initially created by GObject.Object.bind_property() and is owned by the binding.

New in version 2.38.

Property Details

GObject.Binding.props.flags
Name

flags

Type

GObject.BindingFlags

Default Value

GObject.BindingFlags.DEFAULT

Flags

READABLE, WRITABLE, CONSTRUCT_ONLY

Flags to be used to control the GObject.Binding

New in version 2.26.

GObject.Binding.props.source
Name

source

Type

GObject.Object

Default Value

None

Flags

READABLE, WRITABLE, CONSTRUCT_ONLY

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

New in version 2.26.

GObject.Binding.props.source_property
Name

source-property

Type

str

Default Value

None

Flags

READABLE, WRITABLE, CONSTRUCT_ONLY

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

This should be in canonical form to get the best performance.

New in version 2.26.

GObject.Binding.props.target
Name

target

Type

GObject.Object

Default Value

None

Flags

READABLE, WRITABLE, CONSTRUCT_ONLY

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

New in version 2.26.

GObject.Binding.props.target_property
Name

target-property

Type

str

Default Value

None

Flags

READABLE, WRITABLE, CONSTRUCT_ONLY

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

This should be in canonical form to get the best performance.

New in version 2.26.