Struct neon::context::FunctionContext

pub struct FunctionContext<'a> { /* private fields */ }

An execution context of a function call.

The type parameter T is the type of the this-binding.

Implementations

impl<'a> FunctionContext<'a>

pub fn kind(&self) -> CallKind

Indicates whether the function was called with new.

pub fn len(&self) -> usize

Indicates the number of arguments that were passed to the function.

pub fn is_empty(&self) -> bool

Indicates if no arguments were passed to the function.

pub fn argument_opt(&mut self, i: usize) -> Option<Handle<'a, JsValue>>

Produces the ith argument, or None if i is greater than or equal to self.len().

pub fn argument<V: Value>(&mut self, i: usize) -> JsResult<'a, V>

Produces the ith argument and casts it to the type V, or throws an exception if i is greater than or equal to self.len() or cannot be cast to V.

pub fn this<T: Value>(&mut self) -> JsResult<'a, T>

Produces a handle to the this-binding and attempts to downcast as a specific type. Equivalent to calling cx.this_value().downcast_or_throw(&mut cx).

Throws an exception if the value is a different type.

pub fn this_value(&mut self) -> Handle<'a, JsValue>

Produces a handle to the function’s this-binding.

pub fn args<T>(&mut self) -> NeonResult<T>

where T: FromArgs<'a>,

Extract Rust data from the JavaScript arguments.

This is frequently more efficient and ergonomic than getting arguments individually. See the extract module documentation for more examples.

fn add(mut cx: FunctionContext) -> JsResult<JsNumber> {
    let (a, b): (f64, f64) = cx.args()?;

    Ok(cx.number(a + b))
}

pub fn args_opt<T>(&mut self) -> NeonResult<Option<T>>

where T: FromArgs<'a>,

Extract Rust data from the JavaScript arguments.

Similar to FunctionContext::args, but does not throw a JavaScript exception on errors. Useful for function overloading.

fn combine(mut cx: FunctionContext) -> JsResult<JsValue> {
    if let Some((a, b)) = cx.args_opt::<(f64, f64)>()? {
        return Ok(cx.number(a + b).upcast());
    }

    let (a, b): (String, String) = cx.args()?;

    Ok(cx.string(a + &b).upcast())
}

Trait Implementations

impl<'a> Context<'a> for FunctionContext<'a>

fn lock<'b>(&'b mut self) -> Lock<'_, Self>

where 'a: 'b,

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

fn execute_scoped<'b, T, F>(&mut self, f: F) -> T

where F: FnOnce(ExecuteContext<'b>) -> T, 'a: 'b,

Executes a computation in a new memory management scope.

fn compute_scoped<'b, V, F>(&mut self, f: F) -> JsResult<'a, V>

where V: Value, F: FnOnce(ComputeContext<'b>) -> JsResult<'b, V>, 'a: 'b,

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

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>

Convenience method for creating a JsBoolean value.

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

Convenience method for creating a JsNumber value.

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

Convenience method for creating a JsString value.

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

Convenience method for creating a JsString value.

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

Convenience method for creating a JsNull value.

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

Convenience method for creating a JsUndefined value.

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

Convenience method for creating an empty JsObject value.

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

Convenience method for creating an empty JsArray value.

fn array_buffer(&mut self, size: usize) -> JsResult<'a, JsArrayBuffer>

Convenience method for creating an empty JsArrayBuffer value.

fn buffer(&mut self, size: usize) -> JsResult<'a, JsBuffer>

Convenience method for creating an empty JsBuffer value.

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

Available on crate feature napi-5 only.

Convenience method for creating a JsDate value.

fn global<T: Value>(&mut self, name: &str) -> JsResult<'a, T>

Convenience method for looking up a global property by name.

fn global_object(&mut self) -> Handle<'a, JsObject>

Produces a handle to the JavaScript global object.

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

Throws a JS value.

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

Creates a direct instance of the Error class.

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

Creates an instance of the TypeError class.

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

Creates an instance of the RangeError class.

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

Throws a direct instance of the Error class.

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

Throws an instance of the TypeError class.

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

Throws an instance of the RangeError class.

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

Convenience method for wrapping a value in a JsBox.

fn channel(&mut self) -> Channel

Available on crate feature napi-4 only.

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

fn promise(&mut self) -> (Deferred, Handle<'a, JsPromise>)

Creates a Deferred and JsPromise pair. The Deferred handle can be used to resolve or reject the JsPromise.

fn task<'cx, O, E>(&'cx mut self, execute: E) -> TaskBuilder<'_, Self, E>

where O: Send + 'static, E: FnOnce() -> O + Send + 'static, 'a: 'cx,

Creates a TaskBuilder which can be used to schedule the execute callback to asynchronously execute on the Node worker pool.

fn to_raw(&self) -> Env

Available on crate feature sys only.

Gets the raw sys::Env for usage with Node-API.

impl<'a> UnwindSafe for FunctionContext<'a>