Struct Callback

pub struct Callback<T, U = ()> { /* private fields */ }

This is a simplified, reference-counted wrapper around an FnMut(T) -> U Rust closure that may be called from JS when T and U allow.

You can also use the clones! helper macro to clone-capture the environment more ergonomically.

It only supports closures with exactly one input argument and some return value. Memory management is handled by Rust. Whenever Rust drops all clones of the Callback, the closure will be dropped and the function cannot be called from JS anymore.

Use Void to simulate a callback with no arguments.

Implementations

impl<T, U> Callback<T, U>

where T: 'static, U: 'static,

pub fn new(f: impl FnMut(T) -> U + 'static) -> Self

Creates a new Callback from a Rust closure.

pub fn to_closure(&self) -> impl FnMut(T) -> U + 'static

Returns a Rust closure from the callback.

pub fn call(&self, arg: T) -> U

Calls the callback with the given argument.

pub fn premap<V>(&self, f: impl FnMut(V) -> T + 'static) -> Callback<V, U>

where V: 'static,

Returns a new Callback by prepending the given closure to the callback.

pub fn postmap<V>(&self, f: impl FnMut(U) -> V + 'static) -> Callback<T, V>

where V: 'static,

Returns a new Callback by appending the given closure to the callback.

pub fn as_js(&self) -> Ref<'_, JsValue>

where T: FromWasmAbi, U: IntoWasmAbi,

Returns a reference to JsValue of the callback.

impl<T: 'static> Callback<T>

pub fn noop() -> Self

Returns a new Callback that does nothing.

Trait Implementations

impl<T, U> Clone for Callback<T, U>

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T, U> Debug for Callback<T, U>

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

Formats the value using the given formatter.

impl<T, U> Default for Callback<T, U>

where T: 'static, U: Default + 'static,

fn default() -> Self

Returns the “default value” for a type.

impl<F, T, U> From<F> for Callback<T, U>

where F: FnMut(T) -> U + 'static, T: 'static, U: 'static,

fn from(value: F) -> Self

Converts to this type from the input type.

impl<T, U> PartialEq for Callback<T, U>

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, U> Eq for Callback<T, U>