Function leptos_reactive::signal_prelude::create_signal

pub fn create_signal<T>(cx: Scope, value: T) -> (ReadSignal<T>, WriteSignal<T>)

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 a reactive Scope and the initial value as arguments, 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(cx, 0);

// ✅ calling the getter clones and returns the value
assert_eq!(count(), 0);

// ✅ calling the setter sets the value
set_count(1);
assert_eq!(count(), 1);

// ❌ don't try to call the getter within the setter
// set_count(count() + 1);

// ✅ instead, use .update() to mutate the value in place
set_count.update(|count: &mut i32| *count += 1);
assert_eq!(count(), 2);

// ✅ you can create "derived signals" with the same Fn() -> T interface
let double_count = move || count() * 2; // signals are `Copy` so you can `move` them anywhere
set_count(0);
assert_eq!(double_count(), 0);
set_count(1);
assert_eq!(double_count(), 2);