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selector.rs
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selector.rs
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use dioxus_core::prelude::*;
use crate::dependency::Dependency;
use crate::use_signal;
use crate::{get_effect_stack, signal::SignalData, CopyValue, Effect, ReadOnlySignal, Signal};
/// Creates a new Selector. The selector will be run immediately and whenever any signal it reads changes.
///
/// Selectors can be used to efficiently compute derived data from signals.
///
/// ```rust
/// use dioxus::prelude::*;
/// use dioxus_signals::*;
///
/// fn App(cx: Scope) -> Element {
/// let mut count = use_signal(cx, || 0);
/// let double = use_selector(cx, move || count * 2);
/// count += 1;
/// assert_eq!(double.value(), count * 2);
///
/// render! { "{double}" }
/// }
/// ```
pub fn use_selector<R: PartialEq>(
cx: &ScopeState,
f: impl FnMut() -> R + 'static,
) -> ReadOnlySignal<R> {
*cx.use_hook(|| selector(f))
}
/// Creates a new Selector with some local dependencies. The selector will be run immediately and whenever any signal it reads or any dependencies it tracks changes
///
/// Selectors can be used to efficiently compute derived data from signals.
///
/// ```rust
/// use dioxus::prelude::*;
/// use dioxus_signals::*;
///
/// fn App(cx: Scope) -> Element {
/// let mut local_state = use_state(cx, || 0);
/// let double = use_selector_with_dependencies(cx, (local_state.get(),), move |(local_state,)| local_state * 2);
/// local_state.set(1);
///
/// render! { "{double}" }
/// }
/// ```
pub fn use_selector_with_dependencies<R: PartialEq, D: Dependency>(
cx: &ScopeState,
dependencies: D,
mut f: impl FnMut(D::Out) -> R + 'static,
) -> ReadOnlySignal<R>
where
D::Out: 'static,
{
let dependencies_signal = use_signal(cx, || dependencies.out());
let selector = *cx.use_hook(|| {
selector(move || {
let deref = &*dependencies_signal.read();
f(deref.clone())
})
});
let changed = { dependencies.changed(&*dependencies_signal.read()) };
if changed {
dependencies_signal.set(dependencies.out());
}
selector
}
/// Creates a new Selector. The selector will be run immediately and whenever any signal it reads changes.
///
/// Selectors can be used to efficiently compute derived data from signals.
pub fn selector<R: PartialEq>(mut f: impl FnMut() -> R + 'static) -> ReadOnlySignal<R> {
let state = Signal::<R> {
inner: CopyValue::invalid(),
};
let effect = Effect {
source: current_scope_id().expect("in a virtual dom"),
callback: CopyValue::invalid(),
};
{
get_effect_stack().effects.borrow_mut().push(effect);
}
state.inner.value.set(SignalData {
subscribers: Default::default(),
effect_subscribers: Default::default(),
update_any: schedule_update_any().expect("in a virtual dom"),
value: f(),
});
{
get_effect_stack().effects.borrow_mut().pop();
}
effect.callback.value.set(Box::new(move || {
let value = f();
let changed = {
let old = state.inner.read();
value != old.value
};
if changed {
state.set(value)
}
}));
ReadOnlySignal::new(state)
}