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use crate::{node::NodeId, with_runtime, Disposer, Runtime, SignalDispose};
use cfg_if::cfg_if;
use std::{any::Any, cell::RefCell, marker::PhantomData, rc::Rc};
/// Effects run a certain chunk of code whenever the signals they depend on change.
/// `create_effect` queues the given function to run once, tracks its dependence
/// on any signal values read within it, and reruns the function whenever the value
/// of a dependency changes.
///
/// Effects are intended to run *side-effects* of the system, not to synchronize state
/// *within* the system. In other words: don't write to signals within effects, unless
/// you’re coordinating with some other non-reactive side effect.
/// (If you need to define a signal that depends on the value of other signals, use a
/// derived signal or [`create_memo`](crate::create_memo)).
///
/// This first run is queued for the next microtask, i.e., it runs after all other
/// synchronous code has completed. In practical terms, this means that if you use
/// `create_effect` in the body of the component, it will run *after* the view has been
/// created and (presumably) mounted. (If you need an effect that runs immediately, use
/// [`create_render_effect`].)
///
/// The effect function is called with an argument containing whatever value it returned
/// the last time it ran. On the initial run, this is `None`.
///
/// By default, effects **do not run on the server**. This means you can call browser-specific
/// APIs within the effect function without causing issues. If you need an effect to run on
/// the server, use [`create_isomorphic_effect`].
/// ```
/// # use leptos_reactive::*;
/// # use log::*;
/// # let runtime = create_runtime();
/// let (a, set_a) = create_signal(0);
/// let (b, set_b) = create_signal(0);
///
/// // ✅ use effects to interact between reactive state and the outside world
/// create_effect(move |_| {
/// // immediately prints "Value: 0" and subscribes to `a`
/// log::debug!("Value: {}", a.get());
/// });
///
/// set_a.set(1);
/// // ✅ because it's subscribed to `a`, the effect reruns and prints "Value: 1"
///
/// // ❌ don't use effects to synchronize state within the reactive system
/// create_effect(move |_| {
/// // this technically works but can cause unnecessary re-renders
/// // and easily lead to problems like infinite loops
/// set_b.set(a.get() + 1);
/// });
/// # if !cfg!(feature = "ssr") {
/// # assert_eq!(b.get(), 2);
/// # }
/// # runtime.dispose();
/// ```
#[cfg_attr(
any(debug_assertions, feature="ssr"),
instrument(
level = "trace",
skip_all,
fields(
ty = %std::any::type_name::<T>()
)
)
)]
#[track_caller]
#[inline(always)]
pub fn create_effect<T>(f: impl Fn(Option<T>) -> T + 'static) -> Effect<T>
where
T: 'static,
{
cfg_if! {
if #[cfg(not(feature = "ssr"))] {
use crate::{Owner, queue_microtask, with_owner};
let runtime = Runtime::current();
let owner = Owner::current();
let id = runtime.create_effect(f);
queue_microtask(move || {
with_owner(owner.unwrap(), move || {
_ = with_runtime( |runtime| {
runtime.update_if_necessary(id);
});
});
});
Effect { id, ty: PhantomData }
} else {
// clear warnings
_ = f;
Effect { id: Default::default(), ty: PhantomData }
}
}
}
impl<T> Effect<T>
where
T: 'static,
{
/// Effects run a certain chunk of code whenever the signals they depend on change.
/// `create_effect` immediately runs the given function once, tracks its dependence
/// on any signal values read within it, and reruns the function whenever the value
/// of a dependency changes.
///
/// Effects are intended to run *side-effects* of the system, not to synchronize state
/// *within* the system. In other words: don't write to signals within effects.
/// (If you need to define a signal that depends on the value of other signals, use a
/// derived signal or [`create_memo`](crate::create_memo)).
///
/// The effect function is called with an argument containing whatever value it returned
/// the last time it ran. On the initial run, this is `None`.
///
/// By default, effects **do not run on the server**. This means you can call browser-specific
/// APIs within the effect function without causing issues. If you need an effect to run on
/// the server, use [`create_isomorphic_effect`].
/// ```
/// # use leptos_reactive::*;
/// # use log::*;
/// # let runtime = create_runtime();
/// let a = RwSignal::new(0);
/// let b = RwSignal::new(0);
///
/// // ✅ use effects to interact between reactive state and the outside world
/// Effect::new(move |_| {
/// // immediately prints "Value: 0" and subscribes to `a`
/// log::debug!("Value: {}", a.get());
/// });
///
/// a.set(1);
/// // ✅ because it's subscribed to `a`, the effect reruns and prints "Value: 1"
///
/// // ❌ don't use effects to synchronize state within the reactive system
/// Effect::new(move |_| {
/// // this technically works but can cause unnecessary re-renders
/// // and easily lead to problems like infinite loops
/// b.set(a.get() + 1);
/// });
/// # if !cfg!(feature = "ssr") {
/// # assert_eq!(b.get(), 2);
/// # }
/// # runtime.dispose();
/// ```
#[track_caller]
#[inline(always)]
pub fn new(f: impl Fn(Option<T>) -> T + 'static) -> Self {
create_effect(f)
}
/// Creates an effect; unlike effects created by [`create_effect`], isomorphic effects will run on
/// the server as well as the client.
/// ```
/// # use leptos_reactive::*;
/// # use log::*;
/// # let runtime = create_runtime();
/// let a = RwSignal::new(0);
/// let b = RwSignal::new(0);
///
/// // ✅ use effects to interact between reactive state and the outside world
/// Effect::new_isomorphic(move |_| {
/// // immediately prints "Value: 0" and subscribes to `a`
/// log::debug!("Value: {}", a.get());
/// });
///
/// a.set(1);
/// // ✅ because it's subscribed to `a`, the effect reruns and prints "Value: 1"
///
/// // ❌ don't use effects to synchronize state within the reactive system
/// Effect::new_isomorphic(move |_| {
/// // this technically works but can cause unnecessary re-renders
/// // and easily lead to problems like infinite loops
/// b.set(a.get() + 1);
/// });
/// # assert_eq!(b.get(), 2);
/// # runtime.dispose();
#[track_caller]
#[inline(always)]
pub fn new_isomorphic(f: impl Fn(Option<T>) -> T + 'static) -> Self {
create_isomorphic_effect(f)
}
/// Applies the given closure to the most recent value of the effect.
///
/// Because effect functions can return values, each time an effect runs it
/// consumes its previous value. This allows an effect to store additional state
/// (like a DOM node, a timeout handle, or a type that implements `Drop`) and
/// keep it alive across multiple runs.
///
/// This method allows access to the effect’s value outside the effect function.
/// The next time a signal change causes the effect to run, it will receive the
/// mutated value.
pub fn with_value_mut<U>(
&self,
f: impl FnOnce(&mut Option<T>) -> U,
) -> Option<U> {
with_runtime(|runtime| {
let nodes = runtime.nodes.borrow();
let node = nodes.get(self.id)?;
let value = node.value.clone()?;
let mut value = value.borrow_mut();
let value = value.downcast_mut()?;
Some(f(value))
})
.ok()
.flatten()
}
}
/// Creates an effect; unlike effects created by [`create_effect`], isomorphic effects will run on
/// the server as well as the client.
/// ```
/// # use leptos_reactive::*;
/// # use log::*;
/// # let runtime = create_runtime();
/// let (a, set_a) = create_signal(0);
/// let (b, set_b) = create_signal(0);
///
/// // ✅ use effects to interact between reactive state and the outside world
/// create_isomorphic_effect(move |_| {
/// // immediately prints "Value: 0" and subscribes to `a`
/// log::debug!("Value: {}", a.get());
/// });
///
/// set_a.set(1);
/// // ✅ because it's subscribed to `a`, the effect reruns and prints "Value: 1"
///
/// // ❌ don't use effects to synchronize state within the reactive system
/// create_isomorphic_effect(move |_| {
/// // this technically works but can cause unnecessary re-renders
/// // and easily lead to problems like infinite loops
/// set_b.set(a.get() + 1);
/// });
/// # assert_eq!(b.get(), 2);
/// # runtime.dispose();
#[cfg_attr(
any(debug_assertions, feature="ssr"),
instrument(
level = "trace",
skip_all,
fields(
ty = %std::any::type_name::<T>()
)
)
)]
#[track_caller]
#[inline(always)]
pub fn create_isomorphic_effect<T>(
f: impl Fn(Option<T>) -> T + 'static,
) -> Effect<T>
where
T: 'static,
{
let runtime = Runtime::current();
let id = runtime.create_effect(f);
//crate::macros::debug_warn!("creating effect {e:?}");
_ = with_runtime(|runtime| {
runtime.update_if_necessary(id);
});
Effect {
id,
ty: PhantomData,
}
}
/// Creates an effect exactly like [`create_effect`], but runs immediately rather
/// than being queued until the end of the current microtask. This is mostly used
/// inside the renderer but is available for use cases in which scheduling the effect
/// for the next tick is not optimal.
#[cfg_attr(
any(debug_assertions, feature="ssr"),
instrument(
level = "trace",
skip_all,
fields(
ty = %std::any::type_name::<T>()
)
)
)]
#[inline(always)]
pub fn create_render_effect<T>(
f: impl Fn(Option<T>) -> T + 'static,
) -> Effect<T>
where
T: 'static,
{
cfg_if! {
if #[cfg(not(feature = "ssr"))] {
let runtime = Runtime::current();
let id = runtime.create_effect(f);
_ = with_runtime( |runtime| {
runtime.update_if_necessary(id);
});
Effect { id, ty: PhantomData }
} else {
// clear warnings
_ = f;
Effect { id: Default::default(), ty: PhantomData }
}
}
}
/// A handle to an effect, can be used to explicitly dispose of the effect.
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Hash)]
pub struct Effect<T> {
pub(crate) id: NodeId,
ty: PhantomData<T>,
}
impl<T> From<Effect<T>> for Disposer {
fn from(effect: Effect<T>) -> Self {
Disposer(effect.id)
}
}
impl<T> SignalDispose for Effect<T> {
fn dispose(self) {
drop(Disposer::from(self));
}
}
pub(crate) struct EffectState<T, F>
where
T: 'static,
F: Fn(Option<T>) -> T,
{
pub(crate) f: F,
pub(crate) ty: PhantomData<T>,
#[cfg(any(debug_assertions, feature = "ssr"))]
pub(crate) defined_at: &'static std::panic::Location<'static>,
}
pub(crate) trait AnyComputation {
fn run(&self, value: Rc<RefCell<dyn Any>>) -> bool;
}
impl<T, F> AnyComputation for EffectState<T, F>
where
T: 'static,
F: Fn(Option<T>) -> T,
{
#[cfg_attr(
any(debug_assertions, feature = "ssr"),
instrument(
name = "Effect::run()",
level = "trace",
skip_all,
fields(
defined_at = %self.defined_at,
ty = %std::any::type_name::<T>()
)
)
)]
fn run(&self, value: Rc<RefCell<dyn Any>>) -> bool {
// we defensively take and release the BorrowMut twice here
// in case a change during the effect running schedules a rerun
// ideally this should never happen, but this guards against panic
let curr_value = {
// downcast value
let mut value = value.borrow_mut();
let value = value
.downcast_mut::<Option<T>>()
.expect("to downcast effect value");
value.take()
};
// run the effect
let new_value = (self.f)(curr_value);
// set new value
let mut value = value.borrow_mut();
let value = value
.downcast_mut::<Option<T>>()
.expect("to downcast effect value");
*value = Some(new_value);
true
}
}