rs-yew-crate

Installation

SKILL.md

Yew Framework (v0.22)

Yew is a modern Rust framework for creating multi-threaded frontend web applications compiled to WebAssembly. It uses a virtual DOM, component-based architecture, and a JSX-like html! macro. MSRV: Rust 1.84.0.

Project Setup

Prerequisites

rustup target add wasm32-unknown-unknown
cargo install --locked trunk

New Project (manual)

cargo new yew-app && cd yew-app

Cargo.toml:

[package]
name = "yew-app"
version = "0.1.0"
edition = "2021"

[dependencies]
yew = { version = "0.22", features = ["csr"] }

Feature csr enables Renderer and client-side rendering code. Omit for library crates. Use ssr for server-side rendering. Use serde for serde integration on AttrValue.

index.html (project root):

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <title>Yew App</title>
  </head>
  <body></body>
</html>

src/main.rs:

use yew::prelude::*;

#[component]
fn App() -> Html {
    let counter = use_state(|| 0);
    let onclick = {
        let counter = counter.clone();
        move |_| { counter.set(*counter + 1); }
    };

    html! {
        <div>
            <button {onclick}>{ "+1" }</button>
            <p>{ *counter }</p>
        </div>
    }
}

fn main() {
    yew::Renderer::<App>::new().render();
}

trunk serve --open

Starter Template

cargo generate --git https://github.com/yewstack/yew-trunk-minimal-template
trunk serve

Trunk Configuration (Trunk.toml)

[serve]
address = "127.0.0.1"
port = 8080

Function Components

The recommended component model. Annotate with #[component], name in PascalCase, return Html.

use yew::{component, html, Html};

#[component]
fn HelloWorld() -> Html {
    html! { "Hello world" }
}

// Usage:
html! { <HelloWorld /> }

Properties (Props)

Derive Properties + PartialEq. Use AttrValue instead of String for attribute values (cheap to clone).

use yew::{component, html, Html, Properties};

#[derive(Properties, PartialEq)]
pub struct Props {
    pub name: AttrValue,
    #[prop_or_default]
    pub is_loading: bool,
    #[prop_or(AttrValue::Static("default"))]
    pub label: AttrValue,
    #[prop_or_else(|| AttrValue::from("computed"))]
    pub dynamic: AttrValue,
}

#[component]
fn Greeting(&Props { ref name, is_loading, .. }: &Props) -> Html {
    if is_loading { return html! { "Loading" }; }
    html! { <p>{"Hello, "}{name}</p> }
}

// Usage:
html! { <Greeting name="Alice" is_loading=false /> }

Children: Use children: Html field name in props to receive nested content.

#[derive(Properties, PartialEq)]
pub struct ContainerProps {
    pub children: Html,
}

#[component]
fn Container(props: &ContainerProps) -> Html {
    html! { <div class="wrapper">{ props.children.clone() }</div> }
}

Auto-props (yew-autoprops crate): Generate Properties struct from function args.

use yew_autoprops::autoprops;
// #[autoprops] must appear BEFORE #[component]
#[autoprops]
#[component]
fn Greetings(#[prop_or_default] is_loading: bool, message: &AttrValue) -> Html {
    html! { <>{message}</> }
}

Callbacks

Callback<IN, OUT> wraps Fn in Rc. Use Callback::from(|e| ...) for event handlers. Pass down as props for child-to-parent communication.

// Passing callbacks as props
#[derive(Properties, PartialEq)]
pub struct ButtonProps {
    pub on_click: Callback<Video>,
}

// Creating callbacks with state
let selected = use_state(|| None);
let on_select = {
    let selected = selected.clone();
    Callback::from(move |video: Video| selected.set(Some(video)))
};

Hooks

Rules: (1) name starts with use_, (2) call only at top-level of component/hook, (3) same call order every render.

Pre-defined hooks:

use_state / use_state_eq — reactive local state
use_reducer / use_reducer_eq — complex state via reducer pattern
use_effect / use_effect_with — side effects (not run during SSR)
use_memo — memoized computation
use_callback — memoized callback
use_context — consume context value
use_ref / use_mut_ref — persistent mutable reference
use_node_ref — DOM node reference
use_force_update — manual re-render trigger

// State
let counter = use_state(|| 0);
counter.set(*counter + 1);

// Effect with deps (runs when deps change)
{
    let data = data.clone();
    use_effect_with(deps, move |_| {
        // setup logic
        || () // cleanup
    });
}

// Reducer
use yew::prelude::*;

enum Action { Increment, Decrement }
struct State { count: i32 }

impl Reducible for State {
    type Action = Action;
    fn reduce(self: Rc<Self>, action: Action) -> Rc<Self> {
        match action {
            Action::Increment => Self { count: self.count + 1 }.into(),
            Action::Decrement => Self { count: self.count - 1 }.into(),
        }
    }
}

let state = use_reducer(|| State { count: 0 });
state.dispatch(Action::Increment);

Custom hooks: Annotate with #[hook], compose from built-in hooks.

use yew::prelude::*;

#[hook]
pub fn use_toggle(initial: bool) -> (bool, Callback<()>) {
    let state = use_state(move || initial);
    let toggle = {
        let state = state.clone();
        Callback::from(move |_| state.set(!*state))
    };
    (*state, toggle)
}

html! Macro

For detailed syntax rules, element attributes, conditional rendering, fragments, and lists, see references/html_and_events.md.

Key rules:

Single root node required (use <>...</> fragments for multiple)
String literals must be quoted and wrapped in braces: { "text" }
Tags must self-close (<br />) or have matching close tags
Rust expressions go in { ... }
if / if let for conditional rendering
for item in iter { ... } for lists (add key prop)

html! {
    <>
        <h1>{ "Title" }</h1>
        if show_subtitle {
            <p>{ "Subtitle" }</p>
        }
        for item in &items {
            <li key={item.id}>{ &item.name }</li>
        }
    </>
}

Routing

Add yew-router crate. See references/routing.md for nested routers, basename, and query parameters.

use yew::prelude::*;
use yew_router::prelude::*;

#[derive(Clone, Routable, PartialEq)]
enum Route {
    #[at("/")]
    Home,
    #[at("/post/:id")]
    Post { id: String },
    #[not_found]
    #[at("/404")]
    NotFound,
}

fn switch(route: Route) -> Html {
    match route {
        Route::Home => html! { <h1>{"Home"}</h1> },
        Route::Post { id } => html! { <p>{format!("Post {}", id)}</p> },
        Route::NotFound => html! { <h1>{"404"}</h1> },
    }
}

#[component]
fn App() -> Html {
    html! {
        <BrowserRouter>
            <Switch<Route> render={switch} />
        </BrowserRouter>
    }
}

Navigation: <Link<Route> to={Route::Home}>{"Home"}</Link<Route>> or use_navigator() hook.

Contexts

Provide shared state without prop drilling. See references/contexts_and_state.md.

#[derive(Clone, PartialEq)]
struct Theme { foreground: String, background: String }

// Provider
#[component]
fn App() -> Html {
    let theme = Theme { foreground: "#000".into(), background: "#fff".into() };
    html! {
        <ContextProvider<Theme> context={theme}>
            <ThemedButton />
        </ContextProvider<Theme>>
    }
}

// Consumer
#[component]
fn ThemedButton() -> Html {
    let theme = use_context::<Theme>().expect("no theme context");
    html! { <button style={format!("color: {}", theme.foreground)}>{"Click"}</button> }
}

Data Fetching

Use gloo-net for HTTP, serde for deserialization, wasm-bindgen-futures for async.

[dependencies]
yew = { version = "0.22", features = ["csr", "serde"] }
gloo-net = "0.6"
serde = { version = "1.0", features = ["derive"] }
wasm-bindgen-futures = "0.4"

use gloo_net::http::Request;
use yew::prelude::*;

#[component]
fn App() -> Html {
    let data = use_state(Vec::new);
    {
        let data = data.clone();
        use_effect_with((), move |_| {
            let data = data.clone();
            wasm_bindgen_futures::spawn_local(async move {
                let resp: Vec<Item> = Request::get("/api/items")
                    .send().await.unwrap()
                    .json().await.unwrap();
                data.set(resp);
            });
            || ()
        });
    }
    // render data...
    html! {}
}

Events and DOM Interaction

See references/html_and_events.md for full event type table and typed event targets.

// Input handling with TargetCast
use web_sys::HtmlInputElement;
use yew::prelude::*;

#[component]
fn TextInput() -> Html {
    let value = use_state(String::default);
    let oninput = {
        let value = value.clone();
        Callback::from(move |e: InputEvent| {
            let input: HtmlInputElement = e.target_unchecked_into();
            value.set(input.value());
        })
    };
    html! { <input type="text" {oninput} value={(*value).clone()} /> }
}

Server-Side Rendering

See references/ssr.md for SSR setup, hydration, Suspense integration, and component lifecycle during SSR.

Agents (Web Workers)

Offload tasks to web workers for concurrent processing. Use yew-agent crate. Agents support Public (singleton) and Private (per-bridge) modes. Communication via bridges (bidirectional) and dispatchers (unidirectional). Messages serialized with bincode.

Anti-Patterns to Avoid

String in props — Use AttrValue (cheap clone via Rc<str>)
Vec<T> in props — Use IArray<T> from implicit-clone
Interior mutability (RefCell, Mutex) — Yew can't detect changes; use hooks
Side effects in render — Move to use_effect / use_effect_with
Missing keys on lists — Always add key to iterated elements
Accessing Web APIs during SSR — Isolate in use_effect (not run server-side)

Ecosystem & Common Dependencies

Crate	Purpose
`yew-router`	Client-side routing
`gloo`	Ergonomic web APIs (net, timers, storage, events, dialogs)
`gloo-net`	HTTP requests (fetch)
`wasm-bindgen`	Rust ↔ JS interop
`wasm-bindgen-futures`	Async/await in WASM
`web-sys`	Raw Web API bindings
`js-sys`	JavaScript standard built-in bindings
`serde` / `serde_json`	Serialization
`stylist`	CSS-in-Rust
`yewdux`	Redux-like state management
`yew-hooks`	Community hooks collection
`yew-autoprops`	Auto-generate props structs
`bounce`	State management (Redux/Recoil-inspired)
`implicit-clone`	Cheap-clone types (`IString`, `IArray`)

References

HTML macro, events, and DOM interaction: references/html_and_events.md
Routing (yew-router) patterns: references/routing.md
Contexts and state management: references/contexts_and_state.md
Server-side rendering and hydration: references/ssr.md

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