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use std::{
cell::{Ref, RefCell, RefMut},
mem::MaybeUninit,
ops::{Deref, DerefMut},
rc::Rc,
sync::Arc,
};
use dioxus_core::{
prelude::{current_scope_id, has_context, provide_context, schedule_update_any},
ScopeId, ScopeState,
};
use crate::{get_effect_stack, CopyValue, Effect, EffectStack};
/// Creates a new Signal. Signals are a Copy state management solution with automatic dependency tracking.
///
/// ```rust
/// use dioxus::prelude::*;
/// use dioxus_signals::*;
///
/// fn App(cx: Scope) -> Element {
/// let mut count = use_signal(cx, || 0);
///
/// // Because signals have automatic dependency tracking, if you never read them in a component, that component will not be re-rended when the signal is updated.
/// // The app component will never be rerendered in this example.
/// render! { Child { state: count } }
/// }
///
/// #[component]
/// fn Child(cx: Scope, state: Signal<u32>) -> Element {
/// let state = *state;
///
/// use_future!(cx, |()| async move {
/// // Because the signal is a Copy type, we can use it in an async block without cloning it.
/// *state.write() += 1;
/// });
///
/// render! {
/// button {
/// onclick: move |_| *state.write() += 1,
/// "{state}"
/// }
/// }
/// }
/// ```
#[must_use]
pub fn use_signal<T: 'static>(cx: &ScopeState, f: impl FnOnce() -> T) -> Signal<T> {
*cx.use_hook(|| Signal::new(f()))
}
#[derive(Clone)]
struct Unsubscriber {
scope: ScopeId,
subscribers: UnsubscriberArray,
}
type UnsubscriberArray = Rc<RefCell<Vec<Rc<RefCell<Vec<ScopeId>>>>>>;
impl Drop for Unsubscriber {
fn drop(&mut self) {
for subscribers in self.subscribers.borrow().iter() {
subscribers.borrow_mut().retain(|s| *s != self.scope);
}
}
}
fn current_unsubscriber() -> Unsubscriber {
match has_context() {
Some(rt) => rt,
None => {
let owner = Unsubscriber {
scope: current_scope_id().expect("in a virtual dom"),
subscribers: Default::default(),
};
provide_context(owner).expect("in a virtual dom")
}
}
}
pub(crate) struct SignalData<T> {
pub(crate) subscribers: Rc<RefCell<Vec<ScopeId>>>,
pub(crate) effect_subscribers: Rc<RefCell<Vec<Effect>>>,
pub(crate) update_any: Arc<dyn Fn(ScopeId)>,
pub(crate) effect_stack: EffectStack,
pub(crate) value: T,
}
/// Creates a new Signal. Signals are a Copy state management solution with automatic dependency tracking.
///
/// ```rust
/// use dioxus::prelude::*;
/// use dioxus_signals::*;
///
/// #[component]
/// fn App(cx: Scope) -> Element {
/// let mut count = use_signal(cx, || 0);
///
/// // Because signals have automatic dependency tracking, if you never read them in a component, that component will not be re-rended when the signal is updated.
/// // The app component will never be rerendered in this example.
/// render! { Child { state: count } }
/// }
///
/// #[component]
/// fn Child(cx: Scope, state: Signal<u32>) -> Element {
/// let state = *state;
///
/// use_future!(cx, |()| async move {
/// // Because the signal is a Copy type, we can use it in an async block without cloning it.
/// *state.write() += 1;
/// });
///
/// render! {
/// button {
/// onclick: move |_| *state.write() += 1,
/// "{state}"
/// }
/// }
/// }
/// ```
pub struct Signal<T: 'static> {
pub(crate) inner: CopyValue<SignalData<T>>,
}
#[cfg(feature = "serde")]
impl<T: serde::Serialize + 'static> serde::Serialize for Signal<T> {
fn serialize<S: serde::Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
self.read().serialize(serializer)
}
}
#[cfg(feature = "serde")]
impl<'de, T: serde::Deserialize<'de> + 'static> serde::Deserialize<'de> for Signal<T> {
fn deserialize<D: serde::Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
Ok(Self::new(T::deserialize(deserializer)?))
}
}
impl<T: 'static> Signal<T> {
/// Creates a new Signal. Signals are a Copy state management solution with automatic dependency tracking.
pub fn new(value: T) -> Self {
Self {
inner: CopyValue::new(SignalData {
subscribers: Default::default(),
effect_subscribers: Default::default(),
update_any: schedule_update_any().expect("in a virtual dom"),
value,
effect_stack: get_effect_stack(),
}),
}
}
/// Create a new signal with a custom owner scope. The signal will be dropped when the owner scope is dropped instead of the current scope.
pub fn new_in_scope(value: T, owner: ScopeId) -> Self {
Self {
inner: CopyValue::new_in_scope(
SignalData {
subscribers: Default::default(),
effect_subscribers: Default::default(),
update_any: schedule_update_any().expect("in a virtual dom"),
value,
effect_stack: get_effect_stack(),
},
owner,
),
}
}
/// Get the scope the signal was created in.
pub fn origin_scope(&self) -> ScopeId {
self.inner.origin_scope()
}
/// Get the current value of the signal. This will subscribe the current scope to the signal.
/// If the signal has been dropped, this will panic.
pub fn read(&self) -> Ref<T> {
let inner = self.inner.read();
if let Some(effect) = inner.effect_stack.current() {
let mut effect_subscribers = inner.effect_subscribers.borrow_mut();
if !effect_subscribers.contains(&effect) {
effect_subscribers.push(effect);
}
} else if let Some(current_scope_id) = current_scope_id() {
// only subscribe if the vdom is rendering
if dioxus_core::vdom_is_rendering() {
tracing::trace!(
"{:?} subscribed to {:?}",
self.inner.value,
current_scope_id
);
let mut subscribers = inner.subscribers.borrow_mut();
if !subscribers.contains(¤t_scope_id) {
subscribers.push(current_scope_id);
drop(subscribers);
let unsubscriber = current_unsubscriber();
inner.subscribers.borrow_mut().push(unsubscriber.scope);
}
}
}
Ref::map(inner, |v| &v.value)
}
/// Get a mutable reference to the signal's value.
/// If the signal has been dropped, this will panic.
pub fn write(&self) -> Write<'_, T> {
let inner = self.inner.write();
let borrow = RefMut::map(inner, |v| &mut v.value);
Write {
write: borrow,
signal: SignalSubscriberDrop { signal: *self },
}
}
fn update_subscribers(&self) {
{
let inner = self.inner.read();
for &scope_id in &*inner.subscribers.borrow() {
tracing::trace!(
"Write on {:?} triggered update on {:?}",
self.inner.value,
scope_id
);
(inner.update_any)(scope_id);
}
}
let subscribers = {
let self_read = self.inner.read();
let mut effects = self_read.effect_subscribers.borrow_mut();
std::mem::take(&mut *effects)
};
for effect in subscribers {
tracing::trace!(
"Write on {:?} triggered effect {:?}",
self.inner.value,
effect
);
effect.try_run();
}
}
/// Set the value of the signal. This will trigger an update on all subscribers.
pub fn set(&self, value: T) {
*self.write() = value;
}
/// Run a closure with a reference to the signal's value.
/// If the signal has been dropped, this will panic.
pub fn with<O>(&self, f: impl FnOnce(&T) -> O) -> O {
let write = self.read();
f(&*write)
}
/// Run a closure with a mutable reference to the signal's value.
/// If the signal has been dropped, this will panic.
pub fn with_mut<O>(&self, f: impl FnOnce(&mut T) -> O) -> O {
let mut write = self.write();
f(&mut *write)
}
}
impl<T: Clone + 'static> Signal<T> {
/// Get the current value of the signal. This will subscribe the current scope to the signal.
/// If the signal has been dropped, this will panic.
pub fn value(&self) -> T {
self.read().clone()
}
}
impl Signal<bool> {
/// Invert the boolean value of the signal. This will trigger an update on all subscribers.
pub fn toggle(&self) {
self.set(!self.value());
}
}
impl<T: 'static> PartialEq for Signal<T> {
fn eq(&self, other: &Self) -> bool {
self.inner == other.inner
}
}
impl<T> Deref for Signal<T> {
type Target = dyn Fn() -> Ref<'static, T>;
fn deref(&self) -> &Self::Target {
// https://github.com/dtolnay/case-studies/tree/master/callable-types
// First we create a closure that captures something with the Same in memory layout as Self (MaybeUninit<Self>).
let uninit_callable = MaybeUninit::<Self>::uninit();
// Then move that value into the closure. We assume that the closure now has a in memory layout of Self.
let uninit_closure = move || Self::read(unsafe { &*uninit_callable.as_ptr() });
// Check that the size of the closure is the same as the size of Self in case the compiler changed the layout of the closure.
let size_of_closure = std::mem::size_of_val(&uninit_closure);
assert_eq!(size_of_closure, std::mem::size_of::<Self>());
// Then cast the lifetime of the closure to the lifetime of &self.
fn cast_lifetime<'a, T>(_a: &T, b: &'a T) -> &'a T {
b
}
let reference_to_closure = cast_lifetime(
{
// The real closure that we will never use.
&uninit_closure
},
// We transmute self into a reference to the closure. This is safe because we know that the closure has the same memory layout as Self so &Closure == &Self.
unsafe { std::mem::transmute(self) },
);
// Cast the closure to a trait object.
reference_to_closure as &Self::Target
}
}
struct SignalSubscriberDrop<T: 'static> {
signal: Signal<T>,
}
impl<T: 'static> Drop for SignalSubscriberDrop<T> {
fn drop(&mut self) {
self.signal.update_subscribers();
}
}
/// A mutable reference to a signal's value.
pub struct Write<'a, T: 'static, I: 'static = T> {
write: RefMut<'a, T>,
signal: SignalSubscriberDrop<I>,
}
impl<'a, T: 'static, I: 'static> Write<'a, T, I> {
/// Map the mutable reference to the signal's value to a new type.
pub fn map<O>(myself: Self, f: impl FnOnce(&mut T) -> &mut O) -> Write<'a, O, I> {
let Self { write, signal } = myself;
Write {
write: RefMut::map(write, f),
signal,
}
}
/// Try to map the mutable reference to the signal's value to a new type
pub fn filter_map<O>(
myself: Self,
f: impl FnOnce(&mut T) -> Option<&mut O>,
) -> Option<Write<'a, O, I>> {
let Self { write, signal } = myself;
let write = RefMut::filter_map(write, f).ok();
write.map(|write| Write { write, signal })
}
}
impl<'a, T: 'static, I: 'static> Deref for Write<'a, T, I> {
type Target = T;
fn deref(&self) -> &Self::Target {
&self.write
}
}
impl<T, I> DerefMut for Write<'_, T, I> {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.write
}
}
/// A signal that can only be read from.
pub struct ReadOnlySignal<T: 'static> {
inner: Signal<T>,
}
impl<T: 'static> ReadOnlySignal<T> {
/// Create a new read-only signal.
pub fn new(signal: Signal<T>) -> Self {
Self { inner: signal }
}
/// Get the scope that the signal was created in.
pub fn origin_scope(&self) -> ScopeId {
self.inner.origin_scope()
}
/// Get the current value of the signal. This will subscribe the current scope to the signal.
pub fn read(&self) -> Ref<T> {
self.inner.read()
}
/// Run a closure with a reference to the signal's value.
pub fn with<O>(&self, f: impl FnOnce(&T) -> O) -> O {
self.inner.with(f)
}
}
impl<T: Clone + 'static> ReadOnlySignal<T> {
/// Get the current value of the signal. This will subscribe the current scope to the signal.
pub fn value(&self) -> T {
self.read().clone()
}
}
impl<T: 'static> PartialEq for ReadOnlySignal<T> {
fn eq(&self, other: &Self) -> bool {
self.inner == other.inner
}
}
impl<T> Deref for ReadOnlySignal<T> {
type Target = dyn Fn() -> Ref<'static, T>;
fn deref(&self) -> &Self::Target {
// https://github.com/dtolnay/case-studies/tree/master/callable-types
// First we create a closure that captures something with the Same in memory layout as Self (MaybeUninit<Self>).
let uninit_callable = MaybeUninit::<Self>::uninit();
// Then move that value into the closure. We assume that the closure now has a in memory layout of Self.
let uninit_closure = move || Self::read(unsafe { &*uninit_callable.as_ptr() });
// Check that the size of the closure is the same as the size of Self in case the compiler changed the layout of the closure.
let size_of_closure = std::mem::size_of_val(&uninit_closure);
assert_eq!(size_of_closure, std::mem::size_of::<Self>());
// Then cast the lifetime of the closure to the lifetime of &self.
fn cast_lifetime<'a, T>(_a: &T, b: &'a T) -> &'a T {
b
}
let reference_to_closure = cast_lifetime(
{
// The real closure that we will never use.
&uninit_closure
},
// We transmute self into a reference to the closure. This is safe because we know that the closure has the same memory layout as Self so &Closure == &Self.
unsafe { std::mem::transmute(self) },
);
// Cast the closure to a trait object.
reference_to_closure as &Self::Target
}
}