neon/types_impl/extract/
with.rs

1use crate::{
2    context::Cx,
3    result::JsResult,
4    types::{extract::TryIntoJs, Value},
5};
6
7struct With<F>(pub F);
8
9/// Wraps a closure that will be lazily evaluated when [`TryIntoJs::try_into_js`] is
10/// called.
11///
12/// Useful for executing arbitrary code on the main thread before returning from a
13/// function exported with [`neon::export`](crate::export).
14///
15/// **Note:** The return type is [`JsResult`]. If you need to return a non-JavaScript type,
16/// call [`TryIntoJs::try_into_js`].
17///
18/// _See [`With`](With#Example) for example usage._
19///
20/// ## Example
21///
22/// ```
23/// # use neon::{prelude::*, types::extract::{self, TryIntoJs}};
24/// use std::time::Instant;
25///
26/// #[neon::export(task)]
27/// fn sum(nums: Vec<f64>) -> impl for<'cx> TryIntoJs<'cx> {
28///     let start = Instant::now();
29///     let sum = nums.into_iter().sum::<f64>();
30///     let log = format!("sum took {} ms", start.elapsed().as_millis());
31///
32///     extract::with(move |cx| -> NeonResult<_> {
33///         cx.global::<JsObject>("console")?
34///             .method(cx, "log")?
35///             .arg(&log)?
36///             .exec()?;
37///
38///         sum.try_into_js(cx)
39///     })
40/// }
41/// ```
42pub fn with<V, F>(f: F) -> impl for<'cx> TryIntoJs<'cx, Value = V>
43where
44    V: Value,
45    for<'cx> F: FnOnce(&mut Cx<'cx>) -> JsResult<'cx, V>,
46{
47    With(f)
48}
49
50impl<'cx, O, F> TryIntoJs<'cx> for With<F>
51where
52    O: TryIntoJs<'cx>,
53    F: FnOnce(&mut Cx<'cx>) -> O,
54{
55    type Value = O::Value;
56
57    fn try_into_js(self, cx: &mut Cx<'cx>) -> JsResult<'cx, Self::Value> {
58        (self.0)(cx).try_into_js(cx)
59    }
60}
61
62impl<F> super::private::Sealed for With<F> {}
neon/types_impl/extract/with.rs

neon/types_impl/extract/
with.rs
