Yew is a modern Rust framework inspired by Elm and ReactJS.
This framework designed to be compiled into modern browsers' runtimes: wasm, asm.js, emscripten.
Yew implements strict application state management based on messages passing and updates:
type Context = ();
struct Model { }
enum Msg {
DoIt,
}
impl Component<Context> for Model {
// Some details omitted. Explore the examples to get more.
fn update(&mut self, msg: Self::Msg, _: &mut Env<Context, Self>) -> ShouldRender {
match msg {
Msg::DoIt => {
// Update your model on events
}
}
}
}
impl Renderable<Context, Model> for Model {
fn view(&self) -> Html<Context, Self> {
html! {
// Render your model here
<button onclick=|_| Msg::DoIt,>{ "Click me!" }</button>
}
}
}
fn main() {
yew::initialize();
let app: App<_, Model> = App::new(());
app.mount_to_body();
yew::run_loop();
}Predictable mutability and lifetimes (thanks Rust) make possible to reuse an instance of the model and we shouldn't create a new one after every update. It reduces memory allocations.
Feel free to put pure Rust code into HTML tags with all compiler's and borrow checker benefits.
html! {
<section class="todoapp",>
<header class="header",>
<h1>{ "todos" }</h1>
{ view_input(&model) }
</header>
<section class="main",>
<input class="toggle-all",
type="checkbox",
checked=model.is_all_completed(),
onclick=|_| Msg::ToggleAll, />
{ view_entries(&model) }
</section>
</section>
}Yew supports components! You can create a new one by implementing a Component trait
and include it directly into the html! template:
html! {
<nav class="menu",>
<MyButton: title="First Button",/>
<MyButton: title="Second Button",/>
</nav>
}Components lives in Angular-like scopes with parent-to-child (properties) and child-to-parent (events) interaction.
Properties also are pure Rust types with strict checking during compilation.
html! {
<nav class="menu",>
<MyButton: color=Color::Red,/>
<MyButton: onclick=|_| ParentMsg::DoIt,/>
</nav>
}Yew supports fragments: elements without a parent which could be attached somewhere later.
html! {
<>
<tr><td>{ "Row" }</td></tr>
<tr><td>{ "Row" }</td></tr>
<tr><td>{ "Row" }</td></tr>
</>
}Yew framework uses own virtual-dom representation. It updates DOM in a browser
with tiny patches when properties of elements had changed. Every component lives
in own independent loop, interacts with environment (Scope) by messages passing
and supports fine control of rendering.
Set ShouldRender flag to inform the loop when component should be re-rendered:
fn update(&mut self, msg: Self::Msg, _: &mut Env<Context, Self>) -> ShouldRender {
match msg {
Msg::UpdateValue(value) => {
self.value = value;
true
}
Msg::Ignore => {
false
}
}
}It's more effective than compare model after every update, because not every model change leads the changes of the view and we don't need to spend time for comparsion at all. You can control updates very accurately.
Use single-line or multi-line Rust comments inside html-templates.
html! {
<section>
/* Write some ideas
* in multiline comments
*/
<p>{ "and tags could be placed between comments!" }</p>
// <li>{ "or single-line comments" }</li>
</section>
}You can use external crates and put values from them into the template:
extern crate chrono;
use chrono::prelude::*;
impl Renderable<Context, Model> for Model {
fn view(&self) -> Html<Context, Self> {
html! {
<p>{ Local::now() }</p>
}
}
}Some crates hasn't support true wasm target (
wasm32-unknown-unknown) yet.
Pluggable services that allow you to call external APIs like: JavaScript alerts, timeout, storage, fetches and websockets. It's a handy alternative to subscriptions.
Implemented:
IntervalServiceTimeoutServiceStorageServiceDialogServiceFetchServiceWebSocketService
use yew::services::console::ConsoleService;
use yew::services::timeout::TimeoutService;
struct Context {
console: ConsoleService,
timeout: TimeoutService<Msg>,
}
impl Component<Context> for Model {
fn update(&mut self, msg: Self::Msg, context: &mut Env<Context, Self>) -> ShouldRender {
match msg {
Msg::Fire => {
let send_msg = context.send_back(|_| Msg::Timeout);
context.timeout.spawn(Duration::from_secs(5), send_msg);
}
Msg::Timeout => {
context.console.log("Timeout!");
}
}
}
}There is no necessary service? Want to use library from npm?
You can reuse JavaScript libraries with stdweb capabilities and create
own service implementation. For example let's wrap
ccxt library below:
pub struct CcxtService(Option<Value>);
impl CcxtService {
pub fn new() -> Self {
let lib = js! {
return ccxt;
};
CcxtService(Some(lib))
}
pub fn exchanges(&mut self) -> Vec<String> {
let lib = self.0.as_ref().expect("ccxt library object lost");
let v: Value = js! {
var ccxt = @{lib};
console.log(ccxt.exchanges);
return ccxt.exchanges;
};
let v: Vec<String> = v.try_into().expect("can't extract exchanges");
v
}
// Wrap more methods here!
}You could simply choose and use a format of data to store/send and restore/receive it.
Supported: JSON
In development: BSON, TOML, YAML, XML
use yew::format::Json;
#[derive(Serialize, Deserialize)]
struct Client {
first_name: String,
last_name: String,
}
struct Model {
clients: Vec<Client>,
}
impl Component<Context> for Model {
fn update(&mut self, msg: Self::Msg, context: &mut Env<Context, Self>) -> ShouldRender {
Msg::Store => {
// Stores it, but in JSON format/layout
context.local_storage.store(KEY, Json(&model.clients));
}
Msg::Restore => {
// Tries to read and destructure it as JSON formatted data
if let Json(Ok(clients)) = context.local_storage.restore(KEY) {
model.clients = clients;
}
}
}
}Clone or download this repository.
There are many examples to check how the framework works: counter, crm, custom_components, dashboard, fragments, game_of_life, mount_point, npm_and_rest, timer, todomvc, two_apps.
To run them you need to have cargo-web installed as well as a suitable target
for the Rust compiler to generate web output. By default cargo-web uses
asmjs-unknown-emscripten. Install cargo-web and the asmjs emscripten target
as follows:
$ cargo install cargo-web
$ rustup target add asmjs-unknown-emscripten
To start an example enter its directory start it with cargo-web:
$ cargo web start
To run an optimised build instead of a debug build use:
$ cargo web start --release
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