Function leptos_use::sync_signal

pub fn sync_signal<T>(
    left: impl Into<UseRwSignal<T>>,
    right: impl Into<UseRwSignal<T>>
) -> impl Fn() + Clone
where
    T: Clone + PartialEq + 'static,

Two-way Signals synchronization.

Note: Please consider first if you can achieve your goals with the “Good Options” described in the Leptos book firstly. Only if you really have to, use this function. This is in effect the “If you really must…”.

Demo

Link to Demo

Usage

let (a, set_a) = create_signal(1);
let (b, set_b) = create_signal(2);

let stop = sync_signal((a, set_a), (b, set_b));

logging::log!("a: {}, b: {}", a.get(), b.get()); // a: 1, b: 1

set_b.set(3);

logging::log!("a: {}, b: {}", a.get(), b.get()); // a: 3, b: 3

set_a.set(4);

logging::log!("a: {}, b: {}", a.get(), b.get()); // a: 4, b: 4

RwSignal

You can mix and match RwSignals and Signal-WriteSignal pairs.

let (a, set_a) = create_signal(1);
let (b, set_b) = create_signal(2);
let c_rw = create_rw_signal(3);
let d_rw = create_rw_signal(4);

sync_signal((a, set_a), c_rw);
sync_signal(d_rw, (b, set_b));
sync_signal(c_rw, d_rw);

One directional

You can synchronize a signal only from left to right or right to left.

let (a, set_a) = create_signal(1);
let (b, set_b) = create_signal(2);

let stop = sync_signal_with_options(
    (a, set_a),
    (b, set_b),
    SyncSignalOptions::default().direction(SyncDirection::LeftToRight)
);

set_b.set(3); // doesn't sync

logging::log!("a: {}, b: {}", a.get(), b.get()); // a: 1, b: 3

set_a.set(4);

logging::log!("a: {}, b: {}", a.get(), b.get()); // a: 4, b: 4

Custom Transform

You can optionally provide custom transforms between the two signals.

let (a, set_a) = create_signal(10);
let (b, set_b) = create_signal(2);

let stop = sync_signal_with_options(
    (a, set_a),
    (b, set_b),
    SyncSignalOptions::default()
        .transform_ltr(|left| *left * 2)
        .transform_rtl(|right| *right / 2)
);

logging::log!("a: {}, b: {}", a.get(), b.get()); // a: 10, b: 20

set_b.set(30);

logging::log!("a: {}, b: {}", a.get(), b.get()); // a: 15, b: 30

Different Types

SyncSignalOptions::default() is only defined if the two signal types are identical or implement From for each other. Otherwise, you have to initialize the options with with_transforms instead of default.

let options = SyncSignalOptions::with_transforms(
    |left: &String| i32::from_str(left).unwrap_or_default(),
    |right: &i32| right.to_string(),
);