Function leptos::create_signal

source ·
pub fn create_signal<T>(value: T) -> (ReadSignal<T>, WriteSignal<T>)
Expand description

Creates a signal, the basic reactive primitive.

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.

Takes the initial value as an argument, and returns a tuple containing a ReadSignal and a WriteSignal, each of which can be called as a function.

let (count, set_count) = create_signal(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
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);

// ✅ you can create "derived signals" with a Fn() -> T interface
let double_count = move || count.get() * 2; // signals are `Copy` so you can `move` them anywhere
assert_eq!(double_count(), 0);
assert_eq!(double_count(), 2);