将 Vec<RtcIceCandidate> 转换为 JsValue

Question

我正在尝试定义 js_sys::Promise。承诺的解决方案应该 return 一个容器 buf 在 webrtc 初始化中包含所有收集的 ice 候选对象。

let promise = js_sys::Promise::new(&mut |resolve: js_sys::Function, reject: js_sys::Function| {
    let mut buf: Vec<RtcIceCandidate> = Vec::new();
    let onicecandidate_callback = Closure::wrap(
        Box::new(move |ev: RtcPeerConnectionIceEvent| match ev.candidate() {
            Some(candidate) => {
                buf.push(candidate);
            }
            None => {
                // resolve promise here
                resolve.call0(&buf.into())
            }
        }) as Box<dyn FnMut(RtcPeerConnectionIceEvent)>,
    );
});

我不确定如何将 buf 转换为 JsValue which is required to call the resolve 函数。尝试编译上面的代码时出现以下错误：

error[E0277]: the trait bound `wasm_bindgen::JsValue: From<Vec<RtcIceCandidate>>` is not satisfied
   --> src/lib.rs:529:43
    |
529 |                     resolve.call0(&buffer.into());
    |                                           ^^^^ the trait `From<Vec<RtcIceCandidate>>` is not implemented for `wasm_bindgen::JsValue`
    |
    = help: the following implementations were found:
              <wasm_bindgen::JsValue as From<&'a T>>
              <wasm_bindgen::JsValue as From<&'a std::string::String>>
              <wasm_bindgen::JsValue as From<&'a str>>
              <wasm_bindgen::JsValue as From<ArrayBuffer>>
            and 112 others
    = note: required because of the requirements on the impl of `Into<wasm_bindgen::JsValue>` for `Vec<RtcIceCandidate>`

我尝试了一些转换 buf 的替代方法：

resolve.call0(&JsValue::from(&buf));

这给出了错误：

error[E0277]: the trait bound `Vec<RtcIceCandidate>: JsCast` is not satisfied
   --> src/lib.rs:529:36
    |
529 |                     resolve.call0(&JsValue::from(&buffer));
    |                                    ^^^^^^^^^^^^^ the trait `JsCast` is not implemented for `Vec<RtcIceCandidate>`
    |
    = note: required because of the requirements on the impl of `From<&Vec<RtcIceCandidate>>` for `wasm_bindgen::JsValue`

而JsValue::from_serde要求RtcIceCandidate实现Serialize特性，这里不是这种情况。

Answer 1

问题不在于 RtcIceCandidate，即 derefs 到 JsValue。

我从来没有用过js-sys，所以我可能是错的，但问题似乎是必须明确地将Vec转换为js_sys::Array（可能是因为它很昂贵每个元素需要一个 WASM→JS 调用？）。

您可以像这样将 Vec 转换为 JsValue：

&buf.iter().collect::<Array>()

但我怀疑直接使用 Array 会更好。

use js_sys::Array;
use wasm_bindgen::prelude::Closure;
use web_sys::RtcPeerConnectionIceEvent;

fn foo() {
    let _promise = js_sys::Promise::new(
        &mut |resolve: js_sys::Function, _reject: js_sys::Function| {
            let buf: Array = Array::new();
            let _onicecandidate_callback = Closure::wrap(Box::new(
                move |ev: RtcPeerConnectionIceEvent| match ev.candidate() {
                    Some(candidate) => {
                        buf.push(&candidate);
                    }
                    None => {
                        // resolve promise here
                        resolve.call0(&buf).unwrap();
                    }
                },
            )
                as Box<dyn FnMut(RtcPeerConnectionIceEvent)>);
        },
    );
}

还有 Cargo.toml，以防其他人想要复制：

[dependencies]
web-sys = { version = "0.3.56", features = ["RtcIceCandidate", "RtcPeerConnectionIceEvent"] }
js-sys = "0.3.56"
wasm-bindgen = "0.2.79"

将 Vec<RtcIceCandidate> 转换为 JsValue

Converting Vec<RtcIceCandidate> into JsValue

rust

webassembly

web-sys