Struct ReadSignal

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

Expand description

A read-only reactive value.

Unlike the difference between Rust’s shared and mutable-references (&T and &mut), the underlying data is not immutable. The data can be updated with the corresponding Signal (which has mutable access) and will show up in the ReadSignal as well.

A ReadSignal can be simply obtained by dereferencing a Signal. In fact, every Signal is a ReadSignal with additional write abilities!

§Example

let signal: Signal<i32> = create_signal(123);
let read_signal: ReadSignal<i32> = *signal;
assert_eq!(read_signal.get(), 123);
signal.set(456);
assert_eq!(read_signal.get(), 456);
// read_signal.set(789); // <-- This is not allowed!

See create_signal for more information.

Implementations§

§

impl<T> ReadSignal<T>

pub fn is_alive(self) -> bool

Returns true if the signal is still alive, i.e. has not yet been disposed.

pub fn dispose(self)

Disposes the signal, i.e. frees up the memory held on by this signal. Accessing a signal after it has been disposed immediately causes a panic.

pub fn get_untracked(self) -> T
where T: Copy,

Get the value of the signal without tracking it. The type must implement Copy. If this is not the case, use ReadSignal::get_clone_untracked or ReadSignal::with_untracked instead.

§Example

let state = create_signal(0);
// Note that we have used `get_untracked` here so the signal is not actually being tracked
// by the memo.
let doubled = create_memo(move || state.get_untracked() * 2);
state.set(1);
assert_eq!(doubled.get(), 0);

pub fn get_clone_untracked(self) -> T
where T: Clone,

Get the value of the signal without tracking it. The type is Clone-ed automatically.

This is the cloned equivalent of ReadSignal::get_untracked.

pub fn get(self) -> T
where T: Copy,

Get the value of the signal. The type must implement Copy. If this is not the case, use ReadSignal::get_clone_untracked or ReadSignal::with_untracked instead.

When called inside a reactive scope, the signal will be automatically tracked.

§Example

let state = create_signal(0);
assert_eq!(state.get(), 0);

state.set(1);
assert_eq!(state.get(), 1);

// The signal is automatically tracked in the line below.
let doubled = create_memo(move || state.get());

pub fn get_clone(self) -> T
where T: Clone,

Get the value of the signal. The type is Clone-ed automatically.

When called inside a reactive scope, the signal will be automatically tracked.

If the value implements Copy, you should use ReadSignal::get instead.

§Example

let greeting = create_signal("Hello".to_string());
assert_eq!(greeting.get_clone(), "Hello".to_string());

// The signal is automatically tracked in the line below.
let hello_world = create_memo(move || format!("{} World!", greeting.get_clone()));
assert_eq!(hello_world.get_clone(), "Hello World!");

greeting.set("Goodbye".to_string());
assert_eq!(greeting.get_clone(), "Goodbye".to_string());
assert_eq!(hello_world.get_clone(), "Goodbye World!");

pub fn with_untracked(self, f: impl FnOnce(&T) -> U) -> U

Get a value from the signal without tracking it.

pub fn with(self, f: impl FnOnce(&T) -> U) -> U

Get a value from the signal.

When called inside a reactive scope, the signal will be automatically tracked.

pub fn map(self, f: impl FnMut(&T) -> U + 'static) -> ReadSignal

Creates a new memo from this signal and a function. The resulting memo will be created in the current reactive scope.

§Example

let state = create_signal(0);
let doubled = state.map(|val| *val * 2);
assert_eq!(doubled.get(), 0);
state.set(1);
assert_eq!(doubled.get(), 2);

pub fn track(self)

Track the signal in the current reactive scope. This is done automatically when calling ReadSignal::get and other similar methods.

§Example

let state = create_signal(0);
create_effect(move || {
    state.track(); // Track the signal without getting its value.
    println!("Yipee!");
});
state.set(1); // Prints "Yipee!"