Struct AnyView 

pub struct AnyView<State>
where
    State: 'static,
{ /* private fields */ }

A type-erased View: lets a piece of UI change its concrete view type between frames (e.g. a conditional if cond { text(..) } else { button(..) }) while still fitting the statically-typed rebuild machinery.

Rebuild follows the xilem AnyView pattern: the previous view is downcast to detect whether the concrete type is unchanged. Same type → a typed in-place rebuild; different type → the old widget is torn down and a fresh one built and swapped in (signalling LAYOUT | PAINT). Its Element is a Box<dyn Widget>, which implements Widget through the blanket impl so it satisfies View::Element: Widget.

Erasure is idempotent, and the generic builders (child, tuples such as Column((a, b)), ..) accept any View and erase internally, so app code needs AnyView only for stored views, branches of more than eight arms, and genuinely heterogeneous dynamic lists (see any). Branches are written with either(..) (two arms) or EitherOf3..EitherOf8 (three to eight), which keep every arm statically typed and do not erase.

Implementations

impl<State> AnyView<State>

where State: 'static,

pub fn new<V>(view: V) -> AnyView<State>

where V: View<State>,

Erase view into an AnyView.

Erasure is idempotent: if view is already an AnyView<State>, it is returned unchanged — any(any(v)) and AnyView::new(any_view) do not box twice.

Trait Implementations

impl<State> View<State> for AnyView<State>

where State: 'static,

type Element = Box<dyn Widget>

The retained widget this view produces.

fn build( &self, ctx: &mut BuildCtx<'_>, ) -> <AnyView<State> as View<State>>::Element

Materialise a fresh widget for this view.

fn rebuild( &self, prev: &AnyView<State>, element: &mut <AnyView<State> as View<State>>::Element, ctx: &mut BuildCtx<'_>, ) -> ChangeFlags

Reconcile prev (the previous view of the same type) against the live element, mutating it in place and reporting what changed.

fn teardown( &self, element: &mut <AnyView<State> as View<State>>::Element, ctx: &mut BuildCtx<'_>, )

Tear down element when this view is being removed.

fn message(&self, _element: &mut Self::Element, _state: &mut State)

Deliver an event message to this view, mutating application state.