WebAssembly 如何向前端返回一个元组类型？

Question

Rust 代码：

#[wasm_bindgen]
impl CanvasData {
    pub fn index_to_coordinate(&self, index: usize) -> (usize, usize) {
      (index % self.cell_count, index / self.cell_count)
    }
}

CanvasData 是一个保存画布大小的结构体，cell_count 是 usize 类型，这里我将画布所有格子视作一个从左到右，从上到下的一维数组，这个方法的作用就是将数组索引映射成 x, y 坐标。我想返回一个元组，然后在前端这样调用：

const [x, y] = canvasData.index_to_coordinate(100)

不过打包的时候遇到了报错：

wasm-pack build -t web

error[E0277]: the trait bound `(usize, usize): IntoWasmAbi` is not satisfied
[0]   --> src\lib.rs:16:1
[0]    |
[0] 16 | #[wasm_bindgen]
[0]    | ^^^^^^^^^^^^^^^ the trait `IntoWasmAbi` is not implemented for `(usize, usize)`
[0]    |
[0]    = help: the trait `IntoWasmAbi` is implemented for `()`
[0]    = note: required because of the requirements on the impl of `ReturnWasmAbi` for `(usize, usize)`
[0]    = note: this error originates in the attribute macro `wasm_bindgen::prelude::__wasm_bindgen_class_marker` (in Nightly builds, run with -Z macro-backtrace for more info)

如何解决这个错误？

Answer 1

已解决，wasm-bindgen 不支持元组。可以使用元组结构体代替。

详见：How to return a tuple to frontend from wasm?