Struct WeakSceneModel 

pub struct WeakSceneModel(/* private fields */);

A non-owning handle to a Scene — SceneModel without the ownership.

Produced by SceneModel::downgrade and turned back into a SceneModel, for as long as one still exists, by upgrade. Holding one keeps nothing alive.

Its reason to exist is the closure the scene owns: a geometry constraint that captures a SceneModel closes the ring SceneModel → Scene → constraint → SceneModel, and nothing in it is ever dropped. Capturing this instead breaks the ring. See SceneModel::set_geometry_constraint and ProposedChange for the rule and the safe forms.

Implementations

impl WeakSceneModel

pub fn upgrade(&self) -> Option<SceneModel>

An owning handle to the scene, if any still exists.

None once the last SceneModel has been dropped — which is the point: a constraint outliving its scene does nothing instead of keeping it alive.

pub fn is_alive(&self) -> bool

Whether the scene is still alive, without building a handle.

Trait Implementations

impl Clone for WeakSceneModel

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for WeakSceneModel

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.