Trait neon::context::Context[−][src]

pub trait Context<'a>: ContextInternal<'a> {

Show 27 methods    fn lock(&self) -> Lock<'_> { ... }

    fn borrow<'c, V, T, F>(&self, v: &'c Handle<'_, V>, f: F) -> T
    where
        V: Value,
        &'c V: Borrow,
        F: for<'b> FnOnce(Ref<'b, <&'c V as Borrow>::Target>) -> T,
    { ... }

    fn borrow_mut<'c, V, T, F>(&self, v: &'c mut Handle<'_, V>, f: F) -> T
    where
        V: Value,
        &'c mut V: BorrowMut,
        F: for<'b> FnOnce(RefMut<'b, <&'c mut V as Borrow>::Target>) -> T,
    { ... }

    fn execute_scoped<T, F>(&self, f: F) -> T
    where
        F: for<'b> FnOnce(ExecuteContext<'b>) -> T,
    { ... }

    fn compute_scoped<V, F>(&self, f: F) -> JsResult<'a, V>
    where
        V: Value,
        F: for<'b, 'c> FnOnce(ComputeContext<'b, 'c>) -> JsResult<'b, V>,
    { ... }

    fn try_catch<T, F>(&mut self, f: F) -> Result<T, Handle<'a, JsValue>>
    where
        F: FnOnce(&mut Self) -> NeonResult<T>,
    { ... }

    fn boolean(&mut self, b: bool) -> Handle<'a, JsBoolean> { ... }

    fn number<T: Into<f64>>(&mut self, x: T) -> Handle<'a, JsNumber> { ... }

    fn string<S: AsRef<str>>(&mut self, s: S) -> Handle<'a, JsString> { ... }

    fn try_string<S: AsRef<str>>(&mut self, s: S) -> StringResult<'a> { ... }

    fn null(&mut self) -> Handle<'a, JsNull> { ... }

    fn undefined(&mut self) -> Handle<'a, JsUndefined> { ... }

    fn empty_object(&mut self) -> Handle<'a, JsObject> { ... }

    fn empty_array(&mut self) -> Handle<'a, JsArray> { ... }

    fn array_buffer(&mut self, size: u32) -> JsResult<'a, JsArrayBuffer> { ... }

    fn buffer(&mut self, size: u32) -> JsResult<'a, JsBuffer> { ... }

    fn date(
        &mut self, 
        value: impl Into<f64>
    ) -> Result<Handle<'a, JsDate>, DateError> { ... }

    fn global(&mut self) -> Handle<'a, JsObject> { ... }

    fn throw<T: Value, U>(&mut self, v: Handle<'_, T>) -> NeonResult<U> { ... }

    fn error<S: AsRef<str>>(&mut self, msg: S) -> JsResult<'a, JsError> { ... }

    fn type_error<S: AsRef<str>>(&mut self, msg: S) -> JsResult<'a, JsError> { ... }

    fn range_error<S: AsRef<str>>(&mut self, msg: S) -> JsResult<'a, JsError> { ... }

    fn throw_error<S: AsRef<str>, T>(&mut self, msg: S) -> NeonResult<T> { ... }

    fn throw_type_error<S: AsRef<str>, T>(&mut self, msg: S) -> NeonResult<T> { ... }

    fn throw_range_error<S: AsRef<str>, T>(&mut self, msg: S) -> NeonResult<T> { ... }

    fn boxed<U: Finalize + Send + 'static>(
        &mut self, 
        v: U
    ) -> Handle<'a, JsBox<U>> { ... }

    fn channel(&mut self) -> Channel { ... }

}
Expand description

An execution context, which represents the current state of a thread of execution in the JavaScript engine.

All interaction with the JavaScript engine in Neon code is mediated through instances of this trait.

A context has a lifetime 'a, which ensures the safety of handles managed by the JS garbage collector. All handles created during the lifetime of a context are kept alive for that duration and cannot outlive the context.

Provided methods

Lock the JavaScript engine, returning an RAII guard that keeps the lock active as long as the guard is alive.

If this is not the currently active context (for example, if it was used to spawn a scoped context with execute_scoped or compute_scoped), this method will panic.

Convenience method for locking the JavaScript engine and borrowing a single JS value’s internals.

Example:

let b: Handle<JsArrayBuffer> = cx.argument(0)?;
let x: u32 = cx.borrow(&b, |data| { data.as_slice()[0] });
let n: Handle<JsNumber> = cx.number(x);

Note: the borrowed value is required to be a reference to a handle instead of a handle as a workaround for a Rust compiler bug. We may be able to generalize this compatibly in the future when the Rust bug is fixed, but while the extra & is a small ergonomics regression, this API is still a nice convenience.

Convenience method for locking the JavaScript engine and mutably borrowing a single JS value’s internals.

Example:

let mut b: Handle<JsArrayBuffer> = cx.argument(0)?;
cx.borrow_mut(&mut b, |data| {
    let slice = data.as_mut_slice::<u32>();
    slice[0] += 1;
});

Note: the borrowed value is required to be a reference to a handle instead of a handle as a workaround for a Rust compiler bug. We may be able to generalize this compatibly in the future when the Rust bug is fixed, but while the extra &mut is a small ergonomics regression, this API is still a nice convenience.

Executes a computation in a new memory management scope.

Handles created in the new scope are kept alive only for the duration of the computation and cannot escape.

This method can be useful for limiting the life of temporary values created during long-running computations, to prevent leaks.

Executes a computation in a new memory management scope and computes a single result value that outlives the computation.

Handles created in the new scope are kept alive only for the duration of the computation and cannot escape, with the exception of the result value, which is rooted in the outer context.

This method can be useful for limiting the life of temporary values created during long-running computations, to prevent leaks.

This is supported on crate feature try-catch-api only.

Convenience method for creating a JsBoolean value.

Convenience method for creating a JsNumber value.

Convenience method for creating a JsString value.

If the string exceeds the limits of the JS engine, this method panics.

Convenience method for creating a JsString value.

If the string exceeds the limits of the JS engine, this method returns an Err value.

Convenience method for creating a JsNull value.

Convenience method for creating a JsUndefined value.

Convenience method for creating an empty JsObject value.

Convenience method for creating an empty JsArray value.

Convenience method for creating an empty JsArrayBuffer value.

Convenience method for creating an empty JsBuffer value.

This is supported on crate feature napi-5 only.

Convenience method for creating a JsDate value.

Produces a handle to the JavaScript global object.

Throws a JS value.

Creates a direct instance of the Error class.

Creates an instance of the TypeError class.

Creates an instance of the RangeError class.

Throws a direct instance of the Error class.

Throws an instance of the TypeError class.

Throws an instance of the RangeError class.

Convenience method for wrapping a value in a JsBox.

Example:

struct Point(usize, usize);

impl Finalize for Point {}

fn my_neon_function(mut cx: FunctionContext) -> JsResult<JsBox<Point>> {
    let point = cx.boxed(Point(0, 1));

    Ok(point)
}
This is supported on crate features napi-4 and channel-api only.

Returns an unbounded channel for scheduling events to be executed on the JavaScript thread.

When using N-API >= 6,the channel returned by this method is backed by a shared queue. To create a channel backed by a new queue see Channel.

Implementors