Struct CallbackHolder 

pub struct CallbackHolder<F: ?Sized + 'static = dyn FnMut()> { /* private fields */ }

Keeps a composable’s callback parameter across recompositions: its forwarders always call the callback stored last. F is the callback’s trait object, as dyn FnMut(usize).

Implementations

impl<F: ?Sized + 'static> CallbackHolder<F>

pub fn new() -> Self

A holder with no callback yet; its forwarders do nothing until one is stored.

pub fn update_boxed(&self, callback: Box<F>)

Stores callback in place of the one stored last. Generated composable helpers take callbacks type-erased at the public-fn boundary, so helper bodies are compiled once instead of once per caller closure type.

pub fn renders(&self) -> bool

Whether the callback ever ran outside an event handler or an effect: during composition, layout or drawing. A call whose other parameters are unchanged skips its body when its new callbacks never did, because its forwarders call the new ones.

pub fn forwarder(&self) -> CallbackForwarder<F>

The handle a forwarder closure calls the stored callback through.

impl CallbackHolder

pub fn update(&self, callback: impl FnMut() + 'static)

Stores callback in place of the one stored last.

pub fn clone_rc(&self) -> impl Fn() + 'static + use<>

A forwarder that calls the callback stored last.

Trait Implementations

impl<F: ?Sized + 'static> Clone for CallbackHolder<F>

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<F: ?Sized + 'static> Default for CallbackHolder<F>

fn default() -> Self

Returns the “default value” for a type.