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//! Traits and utilities for extract Rust data from JavaScript values | ||
//! | ||
//! The full list of included extractors can be found on [`TryFromJs`]. | ||
//! | ||
//! ## Extracting Handles | ||
//! | ||
//! JavaScript arguments may be extracted into a Rust tuple. | ||
//! | ||
//! ``` | ||
//! # use neon::{prelude::*, types::extract::*}; | ||
//! fn greet(mut cx: FunctionContext) -> JsResult<JsString> { | ||
//! let (greeting, name): (Handle<JsString>, Handle<JsString>) = cx.args()?; | ||
//! let message = format!("{}, {}!", greeting.value(&mut cx), name.value(&mut cx)); | ||
//! | ||
//! Ok(cx.string(message)) | ||
//! } | ||
//! ``` | ||
//! | ||
//! ## Extracting Native Types | ||
//! | ||
//! It's also possible to extract directly into native Rust types instead of a [`Handle`]. | ||
//! | ||
//! ``` | ||
//! # use neon::{prelude::*, types::extract::*}; | ||
//! fn add(mut cx: FunctionContext) -> JsResult<JsNumber> { | ||
//! let (number(a), number(b)) = cx.args()?; | ||
//! | ||
//! Ok(cx.number(a + b)) | ||
//! } | ||
//! ``` | ||
//! | ||
//! ## Extracting [`Option`] | ||
//! | ||
//! It's also possible to mix [`Handle`], Rust types, and even [`Option`] for | ||
//! handling `null` and `undefined`. | ||
//! | ||
//! ``` | ||
//! # use neon::{prelude::*, types::extract::*}; | ||
//! fn get_or_default(mut cx: FunctionContext) -> JsResult<JsValue> { | ||
//! let (Opt::<f64>(n), Val::<JsValue>(default_value)) = cx.args()?; | ||
//! | ||
//! if let Some(n) = n { | ||
//! return Ok(cx.number(n).upcast()); | ||
//! } | ||
//! | ||
//! Ok(default_value) | ||
//! } | ||
//! ``` | ||
//! | ||
//! ## Additional Extractors | ||
//! | ||
//! In some cases, the expected JavaScript type is ambiguous. For example, when | ||
//! trying to extract an [`f64`], the argument may be a `Date` instead of a `number`. | ||
//! Newtype extractors are provided to help. | ||
//! | ||
//! ``` | ||
//! # use neon::{prelude::*, types::extract::*}; | ||
//! # #[cfg(feature = "napi-5")] | ||
//! # use neon::types::JsDate; | ||
//! | ||
//! # #[cfg(feature = "napi-5")] | ||
//! fn add_hours(mut cx: FunctionContext) -> JsResult<JsDate> { | ||
//! const MS_PER_HOUR: f64 = 60.0 * 60.0 * 1000.0; | ||
//! | ||
//! let (Date(date), number(hours)) = cx.args()?; | ||
//! let date = date + hours * MS_PER_HOUR; | ||
//! | ||
//! cx.date(date).or_throw(&mut cx) | ||
//! } | ||
//! ``` | ||
//! | ||
//! ## Overloaded Functions | ||
//! | ||
//! It's common in JavaScript to overload function signatures. This can be implemented with | ||
//! [`FunctionContext::args_opt`] or [`Context::try_catch`]. | ||
//! | ||
//! ``` | ||
//! # use neon::{prelude::*, types::extract::*}; | ||
//! | ||
//! fn add(mut cx: FunctionContext, a: f64, b: f64) -> Handle<JsNumber> { | ||
//! cx.number(a + b) | ||
//! } | ||
//! | ||
//! fn concat(mut cx: FunctionContext, a: String, b: String) -> Handle<JsString> { | ||
//! cx.string(a + &b) | ||
//! } | ||
//! | ||
//! fn combine(mut cx: FunctionContext) -> JsResult<JsValue> { | ||
//! if let Some((a, b)) = cx.args_opt()? { | ||
//! return Ok(add(cx, a, b).upcast()); | ||
//! } | ||
//! | ||
//! let (a, b) = cx.args()?; | ||
//! | ||
//! Ok(concat(cx, a, b).upcast()) | ||
//! } | ||
//! ``` | ||
//! | ||
//! Note well, in this example, type annotations are not required on the tuple because | ||
//! Rust is able to infer it from the type arguments on `add` and `concat`. | ||
use crate::{ | ||
context::{Context, FunctionContext}, | ||
handle::Handle, | ||
result::NeonResult, | ||
types::JsValue, | ||
}; | ||
|
||
pub use self::types::*; | ||
|
||
mod types; | ||
|
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/// Extract Rust data from a JavaScript value | ||
pub trait TryFromJs<'cx>: private::Sealed + Sized { | ||
type Error; | ||
|
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fn try_from_js<C>(cx: &mut C, v: Handle<'cx, JsValue>) -> NeonResult<Result<Self, Self::Error>> | ||
where | ||
C: Context<'cx>; | ||
|
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fn from_js<C>(cx: &mut C, v: Handle<'cx, JsValue>) -> NeonResult<Self> | ||
where | ||
C: Context<'cx>; | ||
} | ||
|
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/// Trait specifying values that may be extracted from function arguments. | ||
/// | ||
/// **Note:** This trait is implemented for tuples of up to 32 values, but for | ||
/// the sake of brevity, only tuples up to size 8 are shown in this documentation. | ||
pub trait FromArgs<'cx>: private::FromArgsInternal<'cx> {} | ||
|
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macro_rules! impl_arguments { | ||
($(#[$attrs:meta])? [$($head:ident),*], []) => {}; | ||
|
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($(#[$attrs:meta])? [$($head:ident),*], [$cur:ident $(, $tail:ident)*]) => { | ||
$(#[$attrs])? | ||
impl<'cx, $($head,)* $cur> FromArgs<'cx> for ($($head,)* $cur,) | ||
where | ||
$($head: TryFromJs<'cx>,)* | ||
$cur: TryFromJs<'cx>, | ||
{} | ||
|
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impl<'cx, $($head,)* $cur> private::FromArgsInternal<'cx> for ($($head,)* $cur,) | ||
where | ||
$($head: TryFromJs<'cx>,)* | ||
$cur: TryFromJs<'cx>, | ||
{ | ||
fn from_args(cx: &mut FunctionContext<'cx>) -> NeonResult<Self> { | ||
#[allow(non_snake_case)] | ||
let [$($head,)* $cur] = cx.argv(); | ||
|
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Ok(( | ||
$($head::from_js(cx, $head)?,)* | ||
$cur::from_js(cx, $cur)?, | ||
)) | ||
} | ||
|
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fn from_args_opt(cx: &mut FunctionContext<'cx>) -> NeonResult<Option<Self>> { | ||
#[allow(non_snake_case)] | ||
let [$($head,)* $cur] = cx.argv(); | ||
|
||
Ok(Some(( | ||
$( | ||
match $head::try_from_js(cx, $head)? { | ||
Ok(v) => v, | ||
Err(_) => return Ok(None), | ||
}, | ||
)* | ||
match $cur::try_from_js(cx, $cur)? { | ||
Ok(v) => v, | ||
Err(_) => return Ok(None), | ||
}, | ||
))) | ||
} | ||
} | ||
|
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impl_arguments!($(#[$attrs])? [$($head,)* $cur], [$($tail),*]); | ||
}; | ||
} | ||
|
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impl_arguments!([], [T1, T2, T3, T4, T5, T6, T7, T8]); | ||
impl_arguments!( | ||
#[doc(hidden)] | ||
[T1, T2, T3, T4, T5, T6, T7, T8], | ||
[ | ||
T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22, T23, T24, T25, T26, | ||
T27, T28, T29, T30, T31, T32 | ||
] | ||
); | ||
|
||
mod private { | ||
use crate::{context::FunctionContext, result::NeonResult}; | ||
|
||
pub trait Sealed {} | ||
|
||
pub trait FromArgsInternal<'cx>: Sized { | ||
fn from_args(cx: &mut FunctionContext<'cx>) -> NeonResult<Self>; | ||
|
||
fn from_args_opt(cx: &mut FunctionContext<'cx>) -> NeonResult<Option<Self>>; | ||
} | ||
} |
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