Function load 

pub fn load<T, P, M>(
    state: impl LoadSource<T, M>,
    ready: impl Fn(Loaded<T>) -> P + 'static,
) -> LoadPiece<T>
where
    T: Clone + 'static,
    P: Piece,

The three states of an async load as three subtrees (docs/async.md): the ready arm, and optional loading and failed arms (nothing is built for a state without an arm). Arms rebuild only when the variant changes; a new ready value updates the ready arm in place through Loaded::get.

load(stations, |s| station_list(s))
    .loading(spinner)
    .failed(|e| label(e.to_string()).secondary())

Whether a refetch passes through Loading is the Resource’s policy; an app that wants its stale content shown during a refresh keeps the last value in its own state and the ready arm reads it.