mirror of
https://github.com/fluencelabs/wasm-bindgen
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67 lines
2.0 KiB
Rust
67 lines
2.0 KiB
Rust
use wasm_bindgen::prelude::*;
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#[wasm_bindgen(start)]
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pub fn run() {
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bare_bones();
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using_a_macro();
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using_web_sys();
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}
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// First up let's take a look of binding `console.log` manually, without the
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// help of `web_sys`. Here we're writing the `#[wasm_bindgen]` annotations
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// manually ourselves, and the correctness of our program relies on the
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// correctness of these annotations!
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#[wasm_bindgen]
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extern "C" {
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// Use `js_namespace` here to bind `console.log(..)` instead of just
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// `log(..)`
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#[wasm_bindgen(js_namespace = console)]
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fn log(s: &str);
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// The `console.log` is quite polymorphic, so we can bind it with multiple
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// signatures. Note that we need to use `js_name` to ensure we always call
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// `log` in JS.
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#[wasm_bindgen(js_namespace = console, js_name = log)]
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fn log_u32(a: u32);
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// Multiple arguments too!
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#[wasm_bindgen(js_namespace = console, js_name = log)]
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fn log_many(a: &str, b: &str);
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}
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fn bare_bones() {
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log("Hello from Rust!");
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log_u32(42);
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log_many("Logging", "many values!");
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}
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// Next let's define a macro that's like `println!`, only it works for
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// `console.log`. Note that `println!` doesn't actually work on the wasm target
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// because the standard library currently just eats all output. To get
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// `println!`-like behavior in your app you'll likely want a macro like this.
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macro_rules! console_log {
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// Note that this is using the `log` function imported above during
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// `bare_bones`
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($($t:tt)*) => (log(&format_args!($($t)*).to_string()))
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}
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fn using_a_macro() {
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console_log!("Hello {}!", "world");
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console_log!("Let's print some numbers...");
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console_log!("1 + 3 = {}", 1 + 3);
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}
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// And finally, we don't even have to define the `log` function ourselves! The
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// `web_sys` crate already has it defined for us.
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fn using_web_sys() {
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use web_sys::console;
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console::log_1(&"Hello using web-sys".into());
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let js: JsValue = 4.into();
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console::log_2(&"Logging arbitrary values looks like".into(), &js);
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}
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