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Merge pull request #1230 from Demonthos/add-computed
Add computed hook
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Original file line number | Diff line number | Diff line change |
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use dioxus_core::{ScopeId, ScopeState}; | ||
use slab::Slab; | ||
use std::{ | ||
cell::{RefCell, RefMut}, | ||
collections::HashSet, | ||
ops::{Deref, DerefMut}, | ||
rc::Rc, | ||
}; | ||
|
||
/// Create a new tracked state. | ||
/// Tracked state is state that can drive Selector state | ||
/// | ||
/// It state will efficiently update any Selector state that is reading from it, but it is not readable on it's own. | ||
/// | ||
/// ```rust | ||
/// use dioxus::prelude::*; | ||
/// | ||
/// fn Parent(cx: Scope) -> Element { | ||
/// let count = use_tracked_state(cx, || 0); | ||
/// | ||
/// render! { | ||
/// Child { | ||
/// count: count.clone(), | ||
/// } | ||
/// } | ||
/// } | ||
/// | ||
/// #[inline_props] | ||
/// fn Child(cx: Scope, count: Tracked<usize>) -> Element { | ||
/// let less_than_five = use_selector(cx, count, |count| *count < 5); | ||
/// | ||
/// render! { | ||
/// "{less_than_five}" | ||
/// } | ||
/// } | ||
/// ``` | ||
pub fn use_tracked_state<T: 'static>(cx: &ScopeState, init: impl FnOnce() -> T) -> &Tracked<T> { | ||
cx.use_hook(|| { | ||
let init = init(); | ||
Tracked::new(cx, init) | ||
}) | ||
} | ||
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||
/// Tracked state is state that can drive Selector state | ||
/// | ||
/// Tracked state will efficiently update any Selector state that is reading from it, but it is not readable on it's own. | ||
#[derive(Clone)] | ||
pub struct Tracked<I> { | ||
state: Rc<RefCell<I>>, | ||
update_any: std::sync::Arc<dyn Fn(ScopeId)>, | ||
subscribers: SubscribedCallbacks<I>, | ||
} | ||
|
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impl<I: PartialEq> PartialEq for Tracked<I> { | ||
fn eq(&self, other: &Self) -> bool { | ||
self.state == other.state | ||
} | ||
} | ||
|
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impl<I> Tracked<I> { | ||
/// Create a new tracked state | ||
pub fn new(cx: &ScopeState, state: I) -> Self { | ||
let subscribers = std::rc::Rc::new(std::cell::RefCell::new(Slab::new())); | ||
Self { | ||
state: Rc::new(RefCell::new(state)), | ||
subscribers, | ||
update_any: cx.schedule_update_any(), | ||
} | ||
} | ||
|
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/// Create a new Selector state from this tracked state | ||
pub fn compute<O: PartialEq + 'static>( | ||
&self, | ||
mut compute: impl FnMut(&I) -> O + 'static, | ||
) -> Selector<O, I> { | ||
let subscribers = Rc::new(RefCell::new(HashSet::new())); | ||
let state = Rc::new(RefCell::new(compute(&self.state.borrow()))); | ||
let update_any = self.update_any.clone(); | ||
|
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Selector { | ||
value: state.clone(), | ||
subscribers: subscribers.clone(), | ||
_tracker: Rc::new(self.track(move |input_state| { | ||
let new = compute(input_state); | ||
let different = { | ||
let state = state.borrow(); | ||
*state != new | ||
}; | ||
if different { | ||
let mut state = state.borrow_mut(); | ||
*state = new; | ||
for id in subscribers.borrow().iter().copied() { | ||
(update_any)(id); | ||
} | ||
} | ||
})), | ||
} | ||
} | ||
|
||
pub(crate) fn track(&self, update: impl FnMut(&I) + 'static) -> Tracker<I> { | ||
let mut subscribers = self.subscribers.borrow_mut(); | ||
let id = subscribers.insert(Box::new(update)); | ||
Tracker { | ||
subscribers: self.subscribers.clone(), | ||
id, | ||
} | ||
} | ||
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/// Write to the tracked state | ||
pub fn write(&self) -> TrackedMut<'_, I> { | ||
TrackedMut { | ||
state: self.state.borrow_mut(), | ||
subscribers: self.subscribers.clone(), | ||
} | ||
} | ||
} | ||
|
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/// A mutable reference to tracked state | ||
pub struct TrackedMut<'a, I> { | ||
state: RefMut<'a, I>, | ||
subscribers: SubscribedCallbacks<I>, | ||
} | ||
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impl<'a, I> Deref for TrackedMut<'a, I> { | ||
type Target = I; | ||
|
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fn deref(&self) -> &Self::Target { | ||
&self.state | ||
} | ||
} | ||
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impl<'a, I> DerefMut for TrackedMut<'a, I> { | ||
fn deref_mut(&mut self) -> &mut Self::Target { | ||
&mut self.state | ||
} | ||
} | ||
|
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impl<'a, I> Drop for TrackedMut<'a, I> { | ||
fn drop(&mut self) { | ||
let state = self.state.deref(); | ||
for (_, sub) in &mut *self.subscribers.borrow_mut() { | ||
sub(state); | ||
} | ||
} | ||
} | ||
|
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type SubscribedCallbacks<I> = std::rc::Rc<std::cell::RefCell<Slab<Box<dyn FnMut(&I) + 'static>>>>; | ||
|
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pub(crate) struct Tracker<I> { | ||
subscribers: SubscribedCallbacks<I>, | ||
id: usize, | ||
} | ||
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impl<I> Drop for Tracker<I> { | ||
fn drop(&mut self) { | ||
let _ = self.subscribers.borrow_mut().remove(self.id); | ||
} | ||
} | ||
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||
pub fn use_selector<I: 'static, O: Clone + PartialEq + 'static>( | ||
cx: &ScopeState, | ||
tracked: &Tracked<I>, | ||
init: impl FnMut(&I) -> O + 'static, | ||
) -> O { | ||
let selector = cx.use_hook(|| tracked.compute(init)); | ||
selector.use_state(cx) | ||
} | ||
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/// Selector state is state that is derived from tracked state | ||
/// | ||
/// Whenever the tracked state changes, the Selector state will be updated and any components reading from it will be rerun | ||
#[derive(Clone)] | ||
pub struct Selector<T, I> { | ||
_tracker: Rc<Tracker<I>>, | ||
value: Rc<RefCell<T>>, | ||
subscribers: Rc<RefCell<HashSet<ScopeId>>>, | ||
} | ||
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impl<T, I> PartialEq for Selector<T, I> { | ||
fn eq(&self, other: &Self) -> bool { | ||
std::rc::Rc::ptr_eq(&self.value, &other.value) | ||
} | ||
} | ||
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impl<T: Clone + PartialEq, I> Selector<T, I> { | ||
/// Read the Selector state and subscribe to updates | ||
pub fn use_state(&self, cx: &ScopeState) -> T { | ||
cx.use_hook(|| { | ||
let id = cx.scope_id(); | ||
self.subscribers.borrow_mut().insert(id); | ||
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ComputedRead { | ||
scope: cx.scope_id(), | ||
subscribers: self.subscribers.clone(), | ||
} | ||
}); | ||
self.value.borrow().clone() | ||
} | ||
} | ||
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struct ComputedRead { | ||
scope: ScopeId, | ||
subscribers: std::rc::Rc<std::cell::RefCell<std::collections::HashSet<ScopeId>>>, | ||
} | ||
|
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impl Drop for ComputedRead { | ||
fn drop(&mut self) { | ||
self.subscribers.borrow_mut().remove(&self.scope); | ||
} | ||
} |
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