Struct WriteSignal

pub struct WriteSignal<T>
where
    T: 'static,
{ /* private fields */ }

The setter for a reactive signal.

A signal is a piece of data that may change over time, and notifies other code when it has changed. This is the core primitive of Leptos’s reactive system.

Calling WriteSignal::update will mutate the signal’s value in place, and notify all subscribers that the signal’s value has changed.

WriteSignal implements Fn, such that set_value(new_value) is equivalent to set_value.update(|value| *value = new_value).

WriteSignal is Copy and 'static, so it can very easily moved into closures or copied structs.

Core Trait Implementations

• .set() (or calling the setter as a function) sets the signal’s value, and notifies all subscribers that the signal’s value has changed. to subscribe to the signal, and to re-run whenever the value of the signal changes.
• .set_untracked() sets the signal’s value without notifying its subscribers.
• .update() mutates the signal’s value in place and notifies all subscribers that the signal’s value has changed.
• .update_untracked() mutates the signal’s value in place without notifying its subscribers.

Examples

let (count, set_count) = create_signal(0);

// ✅ calling the setter sets the value
//    `set_count(1)` on nightly
set_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
set_count.update(|count: &mut i32| *count += 1);
assert_eq!(count.get(), 2);

Trait Implementations

impl<T> Clone for WriteSignal<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> Debug for WriteSignal<T>

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

Formats the value using the given formatter.

impl<T> From<WriteSignal<T>> for SignalSetter<T>

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

Converts to this type from the input type.

impl<T> Hash for WriteSignal<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> PartialEq for WriteSignal<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> SignalDispose for WriteSignal<T>

fn dispose(self)

Disposes of the signal. This:

impl<T> SignalSet for WriteSignal<T>

Examples

let (count, set_count) = create_signal(0);

// notifies subscribers
set_count.update(|n| *n = 1); // it's easier just to call set_count.set(1), though!
assert_eq!(count.get(), 1);

// you can include arbitrary logic in this update function
// also notifies subscribers, even though the value hasn't changed
set_count.update(|n| if *n > 3 { *n += 1 });
assert_eq!(count.get(), 1);

type Value = T

The value held by the signal.

fn set(&self, new_value: T)

Sets the signal’s value and notifies subscribers.

fn try_set(&self, new_value: T) -> Option<T>

Sets the signal’s value and notifies subscribers. Returns None if the signal is still valid, [Some(T)] otherwise.

impl<T> SignalSetUntracked<T> for WriteSignal<T>

where T: 'static,

fn set_untracked(&self, new_value: T)

Sets the signal’s value without notifying dependents.

fn try_set_untracked(&self, new_value: T) -> Option<T>

Attempts to set the signal if it’s still valid. Returns None if the signal was set, [Some(T)] otherwise.

impl<T> SignalUpdate for WriteSignal<T>

Examples

let (count, set_count) = create_signal(0);

// notifies subscribers
set_count.update(|n| *n = 1); // it's easier just to call set_count.set(1), though!
assert_eq!(count.get(), 1);

// you can include arbitrary logic in this update function
// also notifies subscribers, even though the value hasn't changed
set_count.update(|n| if *n > 3 { *n += 1 });
assert_eq!(count.get(), 1);

type Value = T

The value held by the signal.

fn update(&self, f: impl FnOnce(&mut T))

Applies a function to the current value to mutate it in place and notifies subscribers that the signal has changed.

fn try_update<O>(&self, f: impl FnOnce(&mut T) -> O) -> Option<O>

Applies a function to the current value to mutate it in place and notifies subscribers that the signal has changed. Returns [Some(O)] if the signal is still valid, None otherwise.

impl<T> SignalUpdateUntracked<T> for WriteSignal<T>

fn update_untracked(&self, f: impl FnOnce(&mut T))

Runs the provided closure with a mutable reference to the current value without notifying dependents.

fn try_update_untracked<O>(&self, f: impl FnOnce(&mut T) -> O) -> Option<O>

Runs the provided closure with a mutable reference to the current value without notifying dependents and returns the value the closure returned.

impl<T> Copy for WriteSignal<T>

impl<T> Eq for WriteSignal<T>