Struct ArcRwSignal

pub struct ArcRwSignal<T> { /* private fields */ }

A reference-counted signal that can be read from or written to.

A signal is a piece of data that may change over time, and notifies other code when it has changed. This is the atomic unit of reactivity, which begins all other processes of reactive updates.

This is a reference-counted signal, which is Clone but not Copy. For arena-allocated Copy signals, use RwSignal.

Core Trait Implementations

Reading the Value

• .get() clones the current value of the signal. If you call it within an effect, it will cause that effect to subscribe to the signal, and to re-run whenever the value of the signal changes.
  • .get_untracked() clones the value of the signal without reactively tracking it.
• .read() returns a guard that allows accessing the value of the signal by reference. If you call it within an effect, it will cause that effect to subscribe to the signal, and to re-run whenever the value of the signal changes.
  • .read_untracked() gives access to the current value of the signal without reactively tracking it.
• .with() allows you to reactively access the signal’s value without cloning by applying a callback function.
  • .with_untracked() allows you to access the signal’s value by applying a callback function without reactively tracking it.
• .to_stream() converts the signal to an async stream of values.

Updating the Value

• .set() sets the signal to a new value.
• .update() updates the value of the signal by applying a closure that takes a mutable reference.
• .write() returns a guard through which the signal can be mutated, and which notifies subscribers when it is dropped.

Each of these has a related _untracked() method, which updates the signal without notifying subscribers. Untracked updates are not desirable in most cases, as they cause “tearing” between the signal’s value and its observed value. If you want a non-reactive container, used ArenaItem instead.

Examples

let count = ArcRwSignal::new(0);

// ✅ calling the getter clones and returns the value
//    this can be `count()` on nightly
assert_eq!(count.get(), 0);

// ✅ calling the setter sets the value
//    this can be `set_count(1)` on nightly
count.set(1);
assert_eq!(count.get(), 1);

// ❌ you could call the getter within the setter
// set_count.set(count.get() + 1);

// ✅ however it's more efficient to use .update() and mutate the value in place
count.update(|count: &mut i32| *count += 1);
assert_eq!(count.get(), 2);

// ✅ you can create "derived signals" with a Fn() -> T interface
let double_count = {
  // clone before moving into the closure because we use it below
  let count = count.clone();
  move || count.get() * 2
};
count.set(0);
assert_eq!(double_count(), 0);
count.set(1);
assert_eq!(double_count(), 2);

Implementations

impl<T> ArcRwSignal<T>

pub fn new(value: T) -> Self

Creates a new signal, taking the initial value as its argument.

pub fn read_only(&self) -> ArcReadSignal<T>

Returns a read-only handle to the signal.

pub fn write_only(&self) -> ArcWriteSignal<T>

Returns a write-only handle to the signal.

pub fn split(&self) -> (ArcReadSignal<T>, ArcWriteSignal<T>)

Splits the signal into its readable and writable halves.

pub fn unite(read: ArcReadSignal<T>, write: ArcWriteSignal<T>) -> Option<Self>

Reunites the two halves of a signal. Returns None if the two signals provided were not created from the same signal.

Trait Implementations

impl<T> Clone for ArcRwSignal<T>

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T> Debug for ArcRwSignal<T>

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

Formats the value using the given formatter.

impl<T> Default for ArcRwSignal<T>

where T: Default,

fn default() -> Self

Returns the “default value” for a type.

impl<T> DefinedAt for ArcRwSignal<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<'de, T: Deserialize<'de>> Deserialize<'de> for ArcRwSignal<T>

fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<T> Fn() for ArcRwSignal<T>

where ArcRwSignal<T>: Get,

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

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

Performs the call operation.

impl<T> Fn(T) for ArcRwSignal<T>

where ArcRwSignal<T>: Set<Value = T>,

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

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

Performs the call operation.

impl<T> FnMut() for ArcRwSignal<T>

where ArcRwSignal<T>: Get,

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> FnMut(T) for ArcRwSignal<T>

where ArcRwSignal<T>: Set<Value = T>,

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

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

Performs the call operation.

impl<T> FnOnce() for ArcRwSignal<T>

where ArcRwSignal<T>: Get,

type Output = <ArcRwSignal<T> 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<T> FnOnce(T) for ArcRwSignal<T>

where ArcRwSignal<T>: Set<Value = T>,

type Output = ()

The returned type after the call operator is used.

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

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

Performs the call operation.

impl<'a, T> From<&'a ArcRwSignal<T>> for RwSignal<T>

where T: Send + Sync + 'static,

fn from(value: &'a ArcRwSignal<T>) -> Self

Converts to this type from the input type.

impl<T> From<ArcRwSignal<T>> for ArcMemo<T, SyncStorage>

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

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

Converts to this type from the input type.

impl<T: Send + Sync> From<ArcRwSignal<T>> for ArcSignal<T, SyncStorage>

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

Converts to this type from the input type.

impl<T> From<ArcRwSignal<T>> for MaybeSignal<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 RwSignal<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>

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, S> From<RwSignal<T, S>> for ArcRwSignal<T>

where T: 'static, S: Storage<ArcRwSignal<T>>,

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

Converts to this type from the input type.

impl<T> FromLocal<ArcRwSignal<T>> for MaybeSignal<T, LocalStorage>

where T: 'static,

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

Converts between the types.

impl<T> FromLocal<ArcRwSignal<T>> for RwSignal<T, LocalStorage>

where T: 'static,

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

Converts between the types.

impl<T> Hash for ArcRwSignal<T>

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<T> IntoInner for ArcRwSignal<T>

type Value = T

The type of the value contained in the signal.

fn into_inner(self) -> Option<Self::Value>

Returns the inner value if this is the only reference to the signal. Otherwise, returns None and drops this reference.

impl<T> IsDisposed for ArcRwSignal<T>

fn is_disposed(&self) -> bool

If true, the signal cannot be accessed without a panic.

impl<T> Notify for ArcRwSignal<T>

fn notify(&self)

Notifies subscribers of a change in this signal.

impl<T> PartialEq for ArcRwSignal<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: 'static> ReadUntracked for ArcRwSignal<T>

type Value = ReadGuard<T, Plain<T>>

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.

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

This is a backdoor to allow overriding the Read::try_read implementation despite it being auto implemented.

impl<T: Serialize + 'static> Serialize for ArcRwSignal<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: 'static> Write for ArcRwSignal<T>

type Value = T

The type of the signal’s value.

fn try_write(&self) -> Option<impl UntrackableGuard<Target = Self::Value>>

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

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

or None if the signal has already been disposed.

fn write(&self) -> impl UntrackableGuard<Target = Self::Value>

Returns the guard.

fn write_untracked(&self) -> impl DerefMut<Target = Self::Value>

Returns a guard that will not notify subscribers when dropped.

impl<T> Eq for ArcRwSignal<T>