Struct Signal

pub struct Signal<T, S = SyncStorage>
where
    S: Storage<T>,
{ /* private fields */ }

A wrapper for any kind of arena-allocated reactive signal: a ReadSignal, Memo, RwSignal, or derived signal closure, or a plain value of the same type

This allows you to create APIs that take T or any reactive value that returns T as an argument, rather than adding a generic F: Fn() -> T.

Values can be accessed with the same function call, read(), with(), and get() APIs as other signals.

Important Notes about Derived Signals

Signal::derive() is simply a way to box and type-erase a “derived signal,” which is a plain closure that accesses one or more signals. It does not cache the value of that computation. Accessing the value of a Signal<_> that is created using Signal::derive() will run the closure again every time you call .read(), .with(), or .get().

If you want the closure to run the minimal number of times necessary to update its state, and then to cache its value, you should use a Memo (and convert it into a Signal<_>) rather than using Signal::derive().

Note that for many computations, it is nevertheless less expensive to use a derived signal than to create a separate memo and to cache the value: creating a new reactive node and taking the lock on that cached value whenever you access the signal is more expensive than simply re-running the calculation in many cases.

Implementations

impl<T> Signal<T>

where T: Send + Sync + 'static,

pub fn derive(derived_signal: impl Fn() -> T + Send + Sync + 'static) -> Self

Wraps a derived signal, i.e., any computation that accesses one or more reactive signals.

let (count, set_count) = signal(2);
let double_count = Signal::derive(move || count.get() * 2);

// this function takes any kind of wrapped signal
fn above_3(arg: &Signal<i32>) -> bool {
    arg.get() > 3
}

assert_eq!(above_3(&count.into()), false);
assert_eq!(above_3(&double_count), true);

pub fn stored(value: T) -> Self

Moves a static, nonreactive value into a signal, backed by ArcStoredValue.

impl<T> Signal<T, LocalStorage>

where T: 'static,

pub fn derive_local(derived_signal: impl Fn() -> T + 'static) -> Self

Wraps a derived signal. Works like Signal::derive but uses LocalStorage.

pub fn stored_local(value: T) -> Self

Moves a static, nonreactive value into a signal, backed by ArcStoredValue. Works like Signal::stored but uses LocalStorage.

Trait Implementations

impl<T, S> Clone for Signal<T, S>

where S: Storage<T>,

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T, S> Debug for Signal<T, S>

where S: Debug + Storage<T>,

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> Default for Signal<T>

where T: Send + Sync + Default + 'static,

fn default() -> Self

Returns the “default value” for a type.

impl<T> Default for Signal<T, LocalStorage>

where T: Default + 'static,

fn default() -> Self

Returns the “default value” for a type.

impl<T, S> DefinedAt for Signal<T, S>

where S: Storage<T>,

fn defined_at(&self) -> Option<&'static Location<'static>>

Returns the location at which the signal was defined. This is usually simply None in release mode.

impl<T, S> Dispose for Signal<T, S>

where S: Storage<T>,

fn dispose(self)

Disposes of the signal. This:

impl<T, S> Fn() for Signal<T, S>

where Signal<T, S>: Get, S: Storage<T> + Storage<Option<T>> + Storage<SignalTypes<Option<T>, S>>,

extern "rust-call" fn call(&self, _args: ()) -> Self::Output

🔬This is a nightly-only experimental API. (fn_traits)

Performs the call operation.

impl<T, S> FnMut() for Signal<T, S>

where Signal<T, S>: Get, S: Storage<T> + Storage<Option<T>> + Storage<SignalTypes<Option<T>, S>>,

extern "rust-call" fn call_mut(&mut self, _args: ()) -> Self::Output

🔬This is a nightly-only experimental API. (fn_traits)

Performs the call operation.

impl<T, S> FnOnce() for Signal<T, S>

where Signal<T, S>: Get, S: Storage<T> + Storage<Option<T>> + Storage<SignalTypes<Option<T>, S>>,

type Output = <Signal<T, S> as Get>::Value

The returned type after the call operator is used.

extern "rust-call" fn call_once(self, _args: ()) -> Self::Output

🔬This is a nightly-only experimental API. (fn_traits)

Performs the call operation.

impl From<&str> for Signal<Option<String>>

fn from(value: &str) -> Self

Converts to this type from the input type.

impl From<&str> for Signal<Option<String>, LocalStorage>

fn from(value: &str) -> Self

Converts to this type from the input type.

impl From<&str> for Signal<String>

fn from(value: &str) -> Self

Converts to this type from the input type.

impl From<&str> for Signal<String, LocalStorage>

fn from(value: &str) -> Self

Converts to this type from the input type.

impl<T> From<ArcMemo<T>> for Signal<T>

where T: Send + Sync + 'static,

fn from(value: ArcMemo<T>) -> Self

Converts to this type from the input type.

impl<T> From<ArcMemo<T, LocalStorage>> for Signal<T, LocalStorage>

where T: Send + Sync + 'static,

fn from(value: ArcMemo<T, LocalStorage>) -> Self

Converts to this type from the input type.

impl<T> From<ArcReadSignal<T>> for Signal<T>

where T: Send + Sync + 'static,

fn from(value: ArcReadSignal<T>) -> Self

Converts to this type from the input type.

impl<T> From<ArcReadSignal<T>> for Signal<T, LocalStorage>

where T: Send + Sync + 'static,

fn from(value: ArcReadSignal<T>) -> Self

Converts to this type from the input type.

impl<T> From<ArcRwSignal<T>> for Signal<T>

where T: Send + Sync + 'static,

fn from(value: ArcRwSignal<T>) -> Self

Converts to this type from the input type.

impl<T> From<ArcRwSignal<T>> for Signal<T, LocalStorage>

where T: Send + Sync + 'static,

fn from(value: ArcRwSignal<T>) -> Self

Converts to this type from the input type.

impl<T> From<ArcSignal<T>> for Signal<T>

where T: Send + Sync + 'static,

fn from(value: ArcSignal<T, SyncStorage>) -> Self

Converts to this type from the input type.

impl<T> From<MaybeSignal<T>> for Signal<Option<T>>

where T: Clone + Send + Sync + 'static,

fn from(value: MaybeSignal<T>) -> Self

Converts to this type from the input type.

impl<T> From<MaybeSignal<T>> for Signal<T>

where T: Send + Sync + 'static,

fn from(value: MaybeSignal<T>) -> Self

Converts to this type from the input type.

impl<T> From<MaybeSignal<T, LocalStorage>> for Signal<Option<T>, LocalStorage>

where T: Clone + Send + Sync + 'static,

fn from(value: MaybeSignal<T, LocalStorage>) -> Self

Converts to this type from the input type.

impl<T> From<MaybeSignal<T, LocalStorage>> for Signal<T, LocalStorage>

where T: Send + Sync + 'static,

fn from(value: MaybeSignal<T, LocalStorage>) -> Self

Converts to this type from the input type.

impl<T> From<Memo<T>> for Signal<T>

where T: Send + Sync + 'static,

fn from(value: Memo<T>) -> Self

Converts to this type from the input type.

impl<T> From<Memo<T, LocalStorage>> for Signal<T, LocalStorage>

where T: 'static,

fn from(value: Memo<T, LocalStorage>) -> Self

Converts to this type from the input type.

impl<T> From<ReadSignal<T>> for Signal<T>

where T: Send + Sync + 'static,

fn from(value: ReadSignal<T>) -> Self

Converts to this type from the input type.

impl<T> From<ReadSignal<T, LocalStorage>> for Signal<T, LocalStorage>

where T: 'static,

fn from(value: ReadSignal<T, LocalStorage>) -> Self

Converts to this type from the input type.

impl<T> From<RwSignal<T>> for Signal<T>

where T: Send + Sync + 'static,

fn from(value: RwSignal<T>) -> Self

Converts to this type from the input type.

impl<T> From<RwSignal<T, LocalStorage>> for Signal<T, LocalStorage>

where T: 'static,

fn from(value: RwSignal<T, LocalStorage>) -> Self

Converts to this type from the input type.

impl From<Signal<&'static str>> for Signal<Option<String>>

fn from(value: Signal<&'static str>) -> Self

Converts to this type from the input type.

impl From<Signal<&'static str>> for Signal<Option<String>, LocalStorage>

fn from(value: Signal<&'static str>) -> Self

Converts to this type from the input type.

impl From<Signal<&'static str>> for Signal<String>

fn from(value: Signal<&'static str>) -> Self

Converts to this type from the input type.

impl From<Signal<&'static str>> for Signal<String, LocalStorage>

fn from(value: Signal<&'static str>) -> Self

Converts to this type from the input type.

impl From<Signal<Option<&'static str>>> for Signal<Option<String>>

fn from(value: Signal<Option<&'static str>>) -> Self

Converts to this type from the input type.

impl From<Signal<Option<&'static str>>> for Signal<Option<String>, LocalStorage>

fn from(value: Signal<Option<&'static str>>) -> Self

Converts to this type from the input type.

impl<T> From<Signal<Option<T>>> for MaybeProp<T>

where T: Send + Sync, SyncStorage: Storage<Option<T>>,

fn from(value: Signal<Option<T>>) -> Self

Converts to this type from the input type.

impl<T> From<Signal<Option<T>, LocalStorage>> for MaybeProp<T, LocalStorage>

fn from(value: Signal<Option<T>, LocalStorage>) -> Self

Converts to this type from the input type.

impl<T> From<Signal<T>> for MaybeProp<T>

where T: Send + Sync + Clone,

fn from(value: Signal<T>) -> Self

Converts to this type from the input type.

impl<T> From<Signal<T>> for Signal<Option<T>>

where T: Clone + Send + Sync + 'static,

fn from(value: Signal<T>) -> Self

Converts to this type from the input type.

impl<T> From<Signal<T, LocalStorage>> for MaybeProp<T, LocalStorage>

where T: Send + Sync + Clone,

fn from(value: Signal<T, LocalStorage>) -> Self

Converts to this type from the input type.

impl<T> From<Signal<T, LocalStorage>> for Signal<Option<T>, LocalStorage>

where T: Clone + 'static,

fn from(value: Signal<T, LocalStorage>) -> Self

Converts to this type from the input type.

impl<T, S> From<Signal<T, S>> for ArcSignal<T, S>

where S: Storage<SignalTypes<T, S>> + Storage<T>,

fn from(value: Signal<T, S>) -> Self

Converts to this type from the input type.

impl<T, S> From<Signal<T, S>> for MaybeSignal<T, S>

where S: Storage<T>,

fn from(value: Signal<T, S>) -> Self

Converts to this type from the input type.

impl<T> From<T> for Signal<Option<T>>

where T: Send + Sync + 'static,

fn from(value: T) -> Self

Converts to this type from the input type.

impl<T> From<T> for Signal<Option<T>, LocalStorage>

where T: 'static,

fn from(value: T) -> Self

Converts to this type from the input type.

impl<T> From<T> for Signal<T>

where T: Send + Sync + 'static,

fn from(value: T) -> Self

Converts to this type from the input type.

impl<T> From<T> for Signal<T, LocalStorage>

where T: 'static,

fn from(value: T) -> Self

Converts to this type from the input type.

impl<T> FromLocal<ArcSignal<T, LocalStorage>> for Signal<T, LocalStorage>

where T: 'static,

fn from_local(value: ArcSignal<T, LocalStorage>) -> Self

Converts between the types.

impl<T, S> PartialEq for Signal<T, S>

where S: Storage<T>,

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, S> ReadUntracked for Signal<T, S>

where T: 'static, S: Storage<SignalTypes<T, S>> + Storage<T>,

fn custom_try_read(&self) -> Option<Option<Self::Value>>

Overriding the default auto implemented Read::try_read to combine read and track, to avoid 2 clones and just have 1 in the SignalTypes::DerivedSignal.

type Value = ReadGuard<T, SignalReadGuard<T, S>>

The guard type that will be returned, which can be dereferenced to the value.

fn try_read_untracked(&self) -> Option<Self::Value>

Returns the guard, or None if the signal has already been disposed.

fn read_untracked(&self) -> Self::Value

Returns the guard.

impl<T, St> Serialize for Signal<T, St>

where T: Send + Sync + Serialize + 'static, St: Storage<SignalTypes<T, St>> + Storage<T>,

fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl<T, S> Track for Signal<T, S>

where T: 'static, S: Storage<T> + Storage<SignalTypes<T, S>>,

fn track(&self)

Subscribes to this signal in the current reactive scope without doing anything with its value.

impl<T, S> Copy for Signal<T, S>

where S: Storage<T>,

impl<T, S> Eq for Signal<T, S>

where S: Storage<T>,