288 lines
7.9 KiB
Rust
288 lines
7.9 KiB
Rust
#![allow(missing_docs)]
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use dioxus_core::{ScopeState, TaskId};
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use std::{any::Any, cell::Cell, future::Future, rc::Rc, sync::Arc};
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use crate::{use_state, UseState};
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/// A future that resolves to a value.
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///
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/// This runs the future only once - though the future may be regenerated
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/// through the [`UseFuture::restart`] method.
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///
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/// This is commonly used for components that cannot be rendered until some
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/// asynchronous operation has completed.
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///
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/// Whenever the hooks dependencies change, the future will be re-evaluated.
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/// If a future is pending when the dependencies change, the previous future
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/// will be canceled before the new one is started.
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///
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/// - dependencies: a tuple of references to values that are PartialEq + Clone
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#[must_use = "Consider using `cx.spawn` to run a future without reading its value"]
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pub fn use_future<T, F, D>(
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cx: &ScopeState,
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dependencies: D,
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future: impl FnOnce(D::Out) -> F,
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) -> &UseFuture<T>
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where
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T: 'static,
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F: Future<Output = T> + 'static,
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D: UseFutureDep,
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{
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let val = use_state(cx, || None);
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let state = cx.use_hook(move || UseFuture {
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update: cx.schedule_update(),
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needs_regen: Cell::new(true),
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state: val.clone(),
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task: Default::default(),
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dependencies: Vec::new(),
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});
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if dependencies.clone().apply(&mut state.dependencies) || state.needs_regen.get() {
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// kill the old one, if it exists
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if let Some(task) = state.task.take() {
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cx.remove_future(task);
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}
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// Create the new future
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let fut = future(dependencies.out());
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let val = val.clone();
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let task = state.task.clone();
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state.task.set(Some(cx.push_future(async move {
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val.set(Some(fut.await));
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task.take();
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})));
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// Mark that we don't need to regenerate
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state.needs_regen.set(false);
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}
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// update the current value
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state.state.current_val = val.current_val.clone();
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state
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}
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pub enum FutureState<'a, T> {
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Pending,
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Complete(&'a T),
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Regenerating(&'a T), // the old value
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}
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pub struct UseFuture<T: 'static> {
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update: Arc<dyn Fn()>,
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needs_regen: Cell<bool>,
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task: Rc<Cell<Option<TaskId>>>,
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dependencies: Vec<Box<dyn Any>>,
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state: UseState<Option<T>>,
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}
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pub enum UseFutureState<'a, T> {
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Pending,
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Complete(&'a T),
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Reloading(&'a T),
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}
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impl<T> UseFuture<T> {
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/// Restart the future with new dependencies.
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///
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/// Will not cancel the previous future, but will ignore any values that it
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/// generates.
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pub fn restart(&self) {
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self.needs_regen.set(true);
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(self.update)();
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}
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/// Forcefully cancel a future
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pub fn cancel(&self, cx: &ScopeState) {
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if let Some(task) = self.task.take() {
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cx.remove_future(task);
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}
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}
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// Manually set the value in the future slot without starting the future over
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pub fn set(&self, new_value: T) {
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self.state.set(Some(new_value));
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}
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/// Return any value, even old values if the future has not yet resolved.
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///
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/// If the future has never completed, the returned value will be `None`.
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pub fn value(&self) -> Option<&T> {
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self.state.current_val.as_ref().as_ref()
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}
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/// Get the ID of the future in Dioxus' internal scheduler
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pub fn task(&self) -> Option<TaskId> {
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self.task.get()
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}
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/// Get the current state of the future.
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pub fn state(&self) -> UseFutureState<T> {
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match (&self.task.get(), &self.value()) {
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// If we have a task and an existing value, we're reloading
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(Some(_), Some(val)) => UseFutureState::Reloading(val),
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// no task, but value - we're done
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(None, Some(val)) => UseFutureState::Complete(val),
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// no task, no value - something's wrong? return pending
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(None, None) => UseFutureState::Pending,
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// Task, no value - we're still pending
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(Some(_), None) => UseFutureState::Pending,
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}
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}
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}
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pub trait UseFutureDep: Sized + Clone {
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type Out;
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fn out(&self) -> Self::Out;
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fn apply(self, state: &mut Vec<Box<dyn Any>>) -> bool;
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}
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impl UseFutureDep for () {
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type Out = ();
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fn out(&self) -> Self::Out {}
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fn apply(self, _state: &mut Vec<Box<dyn Any>>) -> bool {
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false
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}
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}
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pub trait Dep: 'static + PartialEq + Clone {}
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impl<T> Dep for T where T: 'static + PartialEq + Clone {}
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impl<A: Dep> UseFutureDep for &A {
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type Out = A;
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fn out(&self) -> Self::Out {
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(*self).clone()
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}
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fn apply(self, state: &mut Vec<Box<dyn Any>>) -> bool {
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match state.get_mut(0).and_then(|f| f.downcast_mut::<A>()) {
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Some(val) => {
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if *val != *self {
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*val = self.clone();
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return true;
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}
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}
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None => {
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state.push(Box::new(self.clone()));
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return true;
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}
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}
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false
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}
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}
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macro_rules! impl_dep {
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(
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$($el:ident=$name:ident,)*
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) => {
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impl< $($el),* > UseFutureDep for ($(&$el,)*)
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where
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$(
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$el: Dep
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),*
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{
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type Out = ($($el,)*);
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fn out(&self) -> Self::Out {
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let ($($name,)*) = self;
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($((*$name).clone(),)*)
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}
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#[allow(unused)]
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fn apply(self, state: &mut Vec<Box<dyn Any>>) -> bool {
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let ($($name,)*) = self;
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let mut idx = 0;
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let mut needs_regen = false;
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$(
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match state.get_mut(idx).map(|f| f.downcast_mut::<$el>()).flatten() {
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Some(val) => {
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if *val != *$name {
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*val = $name.clone();
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needs_regen = true;
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}
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}
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None => {
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state.push(Box::new($name.clone()));
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needs_regen = true;
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}
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}
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idx += 1;
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)*
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needs_regen
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}
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}
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};
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}
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impl_dep!(A = a,);
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impl_dep!(A = a, B = b,);
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impl_dep!(A = a, B = b, C = c,);
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impl_dep!(A = a, B = b, C = c, D = d,);
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impl_dep!(A = a, B = b, C = c, D = d, E = e,);
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impl_dep!(A = a, B = b, C = c, D = d, E = e, F = f,);
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impl_dep!(A = a, B = b, C = c, D = d, E = e, F = f, G = g,);
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impl_dep!(A = a, B = b, C = c, D = d, E = e, F = f, G = g, H = h,);
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/// A helper macro that merges uses the closure syntax to elaborate the dependency array
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#[macro_export]
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macro_rules! use_future {
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($cx:ident, || $($rest:tt)*) => { use_future( $cx, (), |_| $($rest)* ) };
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($cx:ident, | $($args:tt),* | $($rest:tt)*) => {
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use_future(
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$cx,
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($($args),*),
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|($($args),*)| $($rest)*
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)
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};
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[allow(unused)]
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#[test]
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fn test_use_future() {
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use dioxus_core::prelude::*;
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struct MyProps {
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a: String,
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b: i32,
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c: i32,
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d: i32,
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e: i32,
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}
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async fn app(cx: Scope<'_, MyProps>) -> Element {
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// should only ever run once
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let fut = use_future(cx, (), |_| async move {});
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// runs when a is changed
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let fut = use_future(cx, (&cx.props.a,), |(a,)| async move {});
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// runs when a or b is changed
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let fut = use_future(cx, (&cx.props.a, &cx.props.b), |(a, b)| async move { 123 });
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let a = use_future!(cx, || async move {
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// do the thing!
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});
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let b = &123;
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let c = &123;
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let a = use_future!(cx, |b, c| async move {
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let a = b + c;
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let blah = "asd";
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});
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todo!()
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}
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}
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}
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