pub struct Closure<T: ?Sized> { /* fields omitted */ }
A handle to both a closure in Rust as well as JS closure which will invoke
the Rust closure.
A Closure
is the primary way that a 'static
lifetime closure is
transferred from Rust to JS. Closure
currently requires that the closures
it's created with have the 'static
lifetime in Rust for soundness reasons.
This type is a "handle" in the sense that whenever it is dropped it will
invalidate the JS closure that it refers to. Any usage of the closure in JS
after the Closure
has been dropped will raise an exception. It's then up
to you to arrange for Closure
to be properly deallocate at an appropriate
location in your program.
The type parameter on Closure
is the type of closure that this represents.
Currently this can only be the Fn
and FnMut
traits with up to 7
arguments (and an optional return value). The arguments/return value of the
trait must be numbers like u32
for now, although this restriction may be
lifted in the future!
Sample usage of Closure
to invoke the setTimeout
API.
#[wasm_bindgen]
extern "C" {
fn setTimeout(closure: &Closure<FnMut()>, time: u32);
#[wasm_bindgen(js_namespace = console)]
fn log(s: &str);
}
#[wasm_bindgen]
pub struct ClosureHandle(Closure<FnMut()>);
#[wasm_bindgen]
pub fn run() -> ClosureHandle {
let cb = Closure::wrap(Box::new(move || {
log("timeout elapsed!");
}) as Box<FnMut()>);
setTimeout(&cb, 1_000);
ClosureHandle(cb)
}
Sample usage of the same example as above except using web_sys
instead
extern crate wasm_bindgen;
extern crate web_sys;
use wasm_bindgen::JsCast;
#[wasm_bindgen]
pub struct ClosureHandle(Closure<FnMut()>);
#[wasm_bindgen]
pub fn run() -> ClosureHandle {
let cb = Closure::wrap(Box::new(move || {
web_sys::console::log_1(&"timeout elapsed!".into());
}) as Box<FnMut()>);
let window = web_sys::window().unwrap();
window.set_timeout_with_callback_and_timeout_and_arguments_0(
cb.as_ref().unchecked_ref(),
1_000,
);
ClosureHandle(cb)
}
A mostly internal function to wrap a boxed closure inside a Closure
type.
This is the function where the JS closure is manufactured.
Leaks this Closure
to ensure it remains valid for the duration of the
entire program.
Note: this function will leak memory. It should be used sparingly
to ensure the memory leak doesn't affect the program too much.
When a Closure
is dropped it will invalidate the associated JS
closure, but this isn't always desired. Some callbacks are alive for
the entire duration of the program, so this can be used to conveniently
leak this instance of Closure
while performing as much internal
cleanup as it can.
The wasm ABI type that this converts into when crossing the ABI boundary. Read more
Convert self
into Self::Abi
so that it can be sent across the wasm ABI boundary. Read more
Executes the destructor for this type. Read more
🔬 This is a nightly-only experimental API. (try_from
)
The type returned in the event of a conversion error.
🔬 This is a nightly-only experimental API. (try_from
)
🔬 This is a nightly-only experimental API. (try_from
)
The type returned in the event of a conversion error.
🔬 This is a nightly-only experimental API. (try_from
)
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more
🔬 This is a nightly-only experimental API. (get_type_id
)
this method will likely be replaced by an associated static