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use self::error::{UseSharedStateError, UseSharedStateResult};
use dioxus_core::{ScopeId, ScopeState};
use std::{collections::HashSet, rc::Rc, sync::Arc};
#[cfg(debug_assertions)]
pub use dioxus_debug_cell::{
error::{BorrowError, BorrowMutError},
Ref, RefCell, RefMut,
};
#[cfg(not(debug_assertions))]
pub use std::cell::{BorrowError, BorrowMutError, Ref, RefCell, RefMut};
#[macro_export]
macro_rules! debug_location {
() => {{
#[cfg(debug_assertions)]
{
std::panic::Location::caller()
}
#[cfg(not(debug_assertions))]
{
()
}
}};
}
pub mod error {
fn locations_display(locations: &[&'static std::panic::Location<'static>]) -> String {
locations
.iter()
.map(|location| format!(" - {location}"))
.collect::<Vec<_>>()
.join("\n")
}
#[derive(thiserror::Error, Debug)]
pub enum UseSharedStateError {
#[cfg_attr(
debug_assertions,
error(
"[{0}] {1} is already borrowed at, so it cannot be borrowed mutably. Previous borrows:\n[{2}]\n\n",
.source.attempted_at,
.type_name,
locations_display(&.source.already_borrowed_at)
)
)]
#[cfg_attr(
not(debug_assertions),
error("{type_name} is already borrowed, so it cannot be borrowed mutably. (More detail available in debug mode)")
)]
AlreadyBorrowed {
source: super::BorrowMutError,
type_name: &'static str,
},
#[cfg_attr(
debug_assertions,
error(
"[{0}] {1} is already borrowed mutably at [{2}], so it cannot be borrowed anymore.",
.source.attempted_at,
.type_name,
locations_display(&.source.already_borrowed_at)
)
)]
#[cfg_attr(
not(debug_assertions),
error("{type_name} is already borrowed mutably, so it cannot be borrowed anymore. (More detail available in debug mode)")
)]
AlreadyBorrowedMutably {
source: super::BorrowError,
type_name: &'static str,
},
}
pub type UseSharedStateResult<T> = Result<T, UseSharedStateError>;
}
type ProvidedState<T> = Rc<RefCell<ProvidedStateInner<T>>>;
// Tracks all the subscribers to a shared State
pub(crate) struct ProvidedStateInner<T> {
value: T,
notify_any: Arc<dyn Fn(ScopeId)>,
consumers: HashSet<ScopeId>,
gen: usize,
}
impl<T> ProvidedStateInner<T> {
pub(crate) fn notify_consumers(&mut self) {
self.gen += 1;
for consumer in self.consumers.iter() {
(self.notify_any)(*consumer);
}
}
}
/// This hook provides some relatively light ergonomics around shared state.
///
/// It is not a substitute for a proper state management system, but it is capable enough to provide use_state - type
/// ergonomics in a pinch, with zero cost.
///
/// # Example
///
/// ```rust
/// # use dioxus::prelude::*;
/// #
/// # fn app(cx: Scope) -> Element {
/// # render! {
/// # Parent{}
/// # }
/// # }
///
/// #[derive(Clone, Copy)]
/// enum Theme {
/// Light,
/// Dark,
/// }
///
/// // Provider
/// fn Parent<'a>(cx: Scope<'a>) -> Element<'a> {
/// use_shared_state_provider(cx, || Theme::Dark);
/// let theme = use_shared_state::<Theme>(cx).unwrap();
///
/// render! {
/// button{
/// onclick: move |_| {
/// let current_theme = *theme.read();
/// *theme.write() = match current_theme {
/// Theme::Dark => Theme::Light,
/// Theme::Light => Theme::Dark,
/// };
/// },
/// "Change theme"
/// }
/// Child{}
/// }
/// }
///
/// // Consumer
/// fn Child<'a>(cx: Scope<'a>) -> Element<'a> {
/// let theme = use_shared_state::<Theme>(cx).unwrap();
/// let current_theme = *theme.read();
///
/// render! {
/// match current_theme {
/// Theme::Dark => {
/// "Dark mode"
/// }
/// Theme::Light => {
/// "Light mode"
/// }
/// }
/// }
/// }
/// ```
///
/// # How it works
///
/// Any time a component calls `write`, every consumer of the state will be notified - excluding the provider.
///
/// Right now, there is not a distinction between read-only and write-only, so every consumer will be notified.
#[must_use]
pub fn use_shared_state<T: 'static>(cx: &ScopeState) -> Option<&UseSharedState<T>> {
let state_owner: &mut Option<UseSharedStateOwner<T>> = &mut *cx.use_hook(move || {
let scope_id = cx.scope_id();
let root = cx.consume_context::<ProvidedState<T>>()?;
root.borrow_mut().consumers.insert(scope_id);
let state = UseSharedState::new(root);
let owner = UseSharedStateOwner { state, scope_id };
Some(owner)
});
state_owner.as_mut().map(|s| {
s.state.gen = s.state.inner.borrow().gen;
&s.state
})
}
/// This wrapper detects when the hook is dropped and will unsubscribe when the component is unmounted
struct UseSharedStateOwner<T> {
state: UseSharedState<T>,
scope_id: ScopeId,
}
impl<T> Drop for UseSharedStateOwner<T> {
fn drop(&mut self) {
// we need to unsubscribe when our component is unmounted
let mut root = self.state.inner.borrow_mut();
root.consumers.remove(&self.scope_id);
}
}
/// State that is shared between components through the context system
pub struct UseSharedState<T> {
pub(crate) inner: Rc<RefCell<ProvidedStateInner<T>>>,
gen: usize,
}
impl<T> UseSharedState<T> {
fn new(inner: Rc<RefCell<ProvidedStateInner<T>>>) -> Self {
let gen = inner.borrow().gen;
Self { inner, gen }
}
/// Notify all consumers of the state that it has changed. (This is called automatically when you call "write")
pub fn notify_consumers(&self) {
self.inner.borrow_mut().notify_consumers();
}
/// Try reading the shared state
#[cfg_attr(debug_assertions, track_caller)]
#[cfg_attr(debug_assertions, inline(never))]
pub fn try_read(&self) -> UseSharedStateResult<Ref<'_, T>> {
match self.inner.try_borrow() {
Ok(value) => Ok(Ref::map(value, |inner| &inner.value)),
Err(source) => Err(UseSharedStateError::AlreadyBorrowedMutably {
source,
type_name: std::any::type_name::<Self>(),
}),
}
}
/// Read the shared value
#[cfg_attr(debug_assertions, track_caller)]
#[cfg_attr(debug_assertions, inline(never))]
pub fn read(&self) -> Ref<'_, T> {
match self.try_read() {
Ok(value) => value,
Err(message) => panic!(
"Reading the shared state failed: {}\n({:?})",
message, message
),
}
}
/// Try writing the shared state
#[cfg_attr(debug_assertions, track_caller)]
#[cfg_attr(debug_assertions, inline(never))]
pub fn try_write(&self) -> UseSharedStateResult<RefMut<'_, T>> {
match self.inner.try_borrow_mut() {
Ok(mut value) => {
value.notify_consumers();
Ok(RefMut::map(value, |inner| &mut inner.value))
}
Err(source) => Err(UseSharedStateError::AlreadyBorrowed {
source,
type_name: std::any::type_name::<Self>(),
}),
}
}
/// Calling "write" will force the component to re-render
///
///
// TODO: We prevent unncessary notifications only in the hook, but we should figure out some more global lock
#[cfg_attr(debug_assertions, track_caller)]
#[cfg_attr(debug_assertions, inline(never))]
pub fn write(&self) -> RefMut<'_, T> {
match self.try_write() {
Ok(value) => value,
Err(message) => panic!(
"Writing to shared state failed: {}\n({:?})",
message, message
),
}
}
/// Tries writing the value without forcing a re-render
#[cfg_attr(debug_assertions, track_caller)]
#[cfg_attr(debug_assertions, inline(never))]
pub fn try_write_silent(&self) -> UseSharedStateResult<RefMut<'_, T>> {
match self.inner.try_borrow_mut() {
Ok(value) => Ok(RefMut::map(value, |inner| &mut inner.value)),
Err(source) => Err(UseSharedStateError::AlreadyBorrowed {
source,
type_name: std::any::type_name::<Self>(),
}),
}
}
/// Writes the value without forcing a re-render
#[cfg_attr(debug_assertions, track_caller)]
#[cfg_attr(debug_assertions, inline(never))]
pub fn write_silent(&self) -> RefMut<'_, T> {
match self.try_write_silent() {
Ok(value) => value,
Err(message) => panic!(
"Writing to shared state silently failed: {}\n({:?})",
message, message
),
}
}
/// Take a reference to the inner value temporarily and produce a new value
#[cfg_attr(debug_assertions, track_caller)]
#[cfg_attr(debug_assertions, inline(never))]
pub fn with<O>(&self, immutable_callback: impl FnOnce(&T) -> O) -> O {
immutable_callback(&*self.read())
}
/// Take a mutable reference to the inner value temporarily and produce a new value
#[cfg_attr(debug_assertions, track_caller)]
#[cfg_attr(debug_assertions, inline(never))]
pub fn with_mut<O>(&self, mutable_callback: impl FnOnce(&mut T) -> O) -> O {
mutable_callback(&mut *self.write())
}
}
impl<T> Clone for UseSharedState<T> {
fn clone(&self) -> Self {
Self {
inner: self.inner.clone(),
gen: self.gen,
}
}
}
impl<T> PartialEq for UseSharedState<T> {
fn eq(&self, other: &Self) -> bool {
self.gen == other.gen
}
}
/// Provide some state for components down the hierarchy to consume without having to drill props. See [`use_shared_state`] to consume the state
///
///
/// # Example
///
/// ```rust
/// # use dioxus::prelude::*;
/// #
/// # fn app(cx: Scope) -> Element {
/// # render! {
/// # Parent{}
/// # }
/// # }
///
/// #[derive(Clone, Copy)]
/// enum Theme {
/// Light,
/// Dark,
/// }
///
/// // Provider
/// fn Parent<'a>(cx: Scope<'a>) -> Element<'a> {
/// use_shared_state_provider(cx, || Theme::Dark);
/// let theme = use_shared_state::<Theme>(cx).unwrap();
///
/// render! {
/// button{
/// onclick: move |_| {
/// let current_theme = *theme.read();
/// *theme.write() = match current_theme {
/// Theme::Dark => Theme::Light,
/// Theme::Light => Theme::Dark,
/// };
/// },
/// "Change theme"
/// }
/// // Children components that consume the state...
/// }
/// }
/// ```
pub fn use_shared_state_provider<T: 'static>(cx: &ScopeState, f: impl FnOnce() -> T) {
cx.use_hook(|| {
let state: ProvidedState<T> = Rc::new(RefCell::new(ProvidedStateInner {
value: f(),
notify_any: cx.schedule_update_any(),
consumers: HashSet::new(),
gen: 0,
}));
cx.provide_context(state);
});
}