yewv

A lightning fast state management module for Yew built with performance and simplicity as a first priority.

Who is this for?

If you wish to use a store alongside Yew fonction components, this library is made for you.

Install

Add the following dependency to your Cargo.toml.

[dependencies]
yewv = "0.2"

Usage

The following need to be respected while using this library:

1. Only works with Yew function components.
2. Store and service contexts must be registered in a parent or root component with ContextProvider.
3. Store and service need to be used in a child component with use_store/use_service.
4. As opposed to map_ref & watch_ref, map & watch are hooks and are therefore constrained to certain rules:
   • Should only be called inside Yew function components.
   • Should not be called inside loops, conditions or callbacks.

Simple app with store

// main.rs
use yew::prelude::*;
use yewv::*;

struct AppState {
    count: i32,
}

#[function_component(App)]
fn app() -> Html {
    let store = StoreContext::new(AppState { count: 0 });
    html! {
        <ContextProvider<StoreContext<AppState>> context={store}>
            <Counter />
            <Counter />
        </ContextProvider<StoreContext<AppState>>>
    }
}

#[function_component(Counter)]
fn counter() -> Html {
    let store = use_store::<AppState>();
    let count = store.map_ref(|state| &state.count);
    let onclick = {
        let store = store.clone();
        move |_| {
            let state = store.state();
            store.set_state(AppState {
                count: state.count + 1,
            });
        }
    };
    html! {
        <button {onclick}>{format!("{} +", count)}</button>
    }
}

fn main() {
    yew::start_app::<App>();
}

Simple app with store and service

// main.rs
use yew::prelude::*;
use yewv::*;

struct AppState {
    count: i32,
}

struct AppService {
    store: StoreContext<AppState>,
}

impl AppService {
    fn increment_count(&self) {
        let state = self.store.state();
        self.store.set_state(AppState {
            count: state.count + 1,
        });
    }
}

#[function_component(App)]
fn app() -> Html {
    let store = StoreContext::new(AppState { count: 0 });
    let service = ServiceContext::new(AppService {
        store: store.clone(),
    });
    html! {
        <ContextProvider<StoreContext<AppState>> context={store}>
        <ContextProvider<ServiceContext<AppService>> context={service}>
            <Counter />
            <Counter />
        </ContextProvider<ServiceContext<AppService>>>
        </ContextProvider<StoreContext<AppState>>>
    }
}

#[function_component(Counter)]
fn counter() -> Html {
    let service = use_service::<AppService>();
    let store = use_store::<AppState>();

    let count = store.map_ref(|state| &state.count);
    let onclick = move |_| service.increment_count();

    html! {
        <button {onclick}>{format!("{} +", count)}</button>
    }
}

fn main() {
    yew::start_app::<App>();
}

map vs map_ref

If you only wish to reference a value owned by the store, you should use map_ref. As opposed to map, map_ref doesn't take ownership of the referenced value. It is usually preferable to use map_ref over map when possible. However, it is not always possible to use map_ref. For instance, if the value you wish to access is not owned by the store state, you will need to use map:

let length = store.map(|state| state.some_vector.len());

Why is it so fast?

Custom hooks

The store utilizes highly optimized custom hooks for better performance and memory efficiency.

Renders only when and where needed

Subscriptions done to the store with map, map_ref, watch and watch_ref will only trigger a render on the component if the observed value has changed.

Reference VS Ownership

Instead of propagating clone/copy of the application state throughout components, references are used.

Good practices

Reference only what's needed

When you are observing a value in a store, make sure you are not taking more than necessary. For instance, if you are only interested in a single value from a vector, there is no need to reference the entire vector:

let first = store.map_ref(|state| &state.some_vector[0]);
let last = store.map_ref(|state| state.some_vector.iter().last().expect("to have a value"));

Segregation of stores in large applications

When and where it makes sense, try to break your monolithic stores into multiple. Doing so will improve the performance of the application as a whole.

Credits

• Rust - MIT or Apache-2.0
• Yew - MIT or Apache-2.0