Struct neon::event::Channel

source ·
pub struct Channel { /* private fields */ }
Available on crate feature napi-4 only.
Expand description

Channel for scheduling Rust closures to execute on the JavaScript main thread.

Cloning a Channel will create a new channel that shares a backing queue for events.

Example

The following example spawns a standard Rust thread to complete a computation and calls back to a JavaScript function asynchronously with the result.

fn async_fibonacci(mut cx: FunctionContext) -> JsResult<JsUndefined> {
    // These types (`f64`, `Root<JsFunction>`, `Channel`) may all be sent
    // across threads.
    let n = cx.argument::<JsNumber>(0)?.value(&mut cx);
    let callback = cx.argument::<JsFunction>(1)?.root(&mut cx);
    let channel = cx.channel();

    // Spawn a thread to complete the execution. This will _not_ block the
    // JavaScript event loop.
    std::thread::spawn(move || {
        let result = fibonacci(n);

        // Send a closure as a task to be executed by the JavaScript event
        // loop. This _will_ block the event loop while executing.
        channel.send(move |mut cx| {
            let callback = callback.into_inner(&mut cx);
            let this = cx.undefined();
            let args = vec![
                cx.null().upcast::<JsValue>(),
                cx.number(result).upcast(),
            ];

            callback.call(&mut cx, this, args)?;

            Ok(())
        });
    });

    Ok(cx.undefined())
}

Implementations§

Creates an unbounded channel for scheduling closures on the JavaScript main thread

Allow the Node event loop to exit while this Channel exists. Idempotent

Prevent the Node event loop from exiting while this Channel exists. (Default) Idempotent

Schedules a closure to execute on the JavaScript thread that created this Channel Panics if there is a libuv error

Schedules a closure to execute on the JavaScript thread that created this Channel Returns an Error if the task could not be scheduled.

See SendError for additional details on failure causes.

Returns a boolean indicating if this Channel will prevent the Node event loop from exiting.

Trait Implementations§

Returns a clone of the Channel instance that shares the internal unbounded queue with the original channel. Scheduling callbacks on the same queue is faster than using separate channels, but might lead to starvation if one of the threads posts significantly more callbacks on the channel than the other one.

Cloned and referenced Channel instances might trigger additional event-loop tick when dropped. Channel can be wrapped into an Arc and shared between different threads/callers to avoid this.

Performs copy-assignment from source. Read more
Formats the value using the given formatter. Read more
Executes the destructor for this type. Read more

Auto Trait Implementations§

Blanket Implementations§

Gets the TypeId of self. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The resulting type after obtaining ownership.
Creates owned data from borrowed data, usually by cloning. Read more
Uses borrowed data to replace owned data, usually by cloning. Read more
The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.