smart-house-web: leptos эсперименты
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#![allow(non_snake_case)]
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use leptos::ev::SubmitEvent;
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use leptos::prelude::*;
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// Iteration is a very common task in most applications.
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// So how do you take a list of data and render it in the DOM?
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// This example will show you the two ways:
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// 1) for mostly-static lists, using Rust iterators
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// 2) for lists that grow, shrink, or move items, using <For/>
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#[component]
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fn App() -> impl IntoView {
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view! {
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<h1>"Iteration"</h1>
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<h2>"Static List"</h2>
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<p>"Use this pattern if the list itself is static."</p>
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<StaticList length=5/>
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<h2>"Dynamic List"</h2>
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<p>"Use this pattern if the rows in your list will change."</p>
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<DynamicList initial_length=5/>
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<h2>"Controlled Component"</h2>
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<ControlledComponent/>
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<h2>"Uncontrolled Component"</h2>
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<UncontrolledComponent/>
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}
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}
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/// A list of counters, without the ability
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/// to add or remove any.
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#[component]
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fn StaticList(
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/// How many counters to include in this list.
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length: usize,
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) -> impl IntoView {
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// create counter signals that start at incrementing numbers
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let counters = (1..=length).map(|idx| RwSignal::new(idx));
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fn ControlledComponent() -> impl IntoView {
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// create a signal to hold the value
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let (name, set_name) = signal("Controlled".to_string());
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// when you have a list that doesn't change, you can
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// manipulate it using ordinary Rust iterators
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// and collect it into a Vec<_> to insert it into the DOM
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let counter_buttons = counters
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.map(|count| {
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view! {
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<li>
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<button
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on:click=move |_| *count.write() += 1
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>
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{count}
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</button>
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</li>
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<input type="text"
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// fire an event whenever the input changes
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// adding :target after the event gives us access to
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// a correctly-typed element at ev.target()
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on:input:target=move |ev| {
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set_name.set(ev.target().value());
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}
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})
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.collect::<Vec<_>>();
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// Note that if `counter_buttons` were a reactive list
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// and its value changed, this would be very inefficient:
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// it would rerender every row every time the list changed.
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view! {
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<ul>{counter_buttons}</ul>
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// the `prop:` syntax lets you update a DOM property,
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// rather than an attribute.
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//
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// IMPORTANT: the `value` *attribute* only sets the
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// initial value, until you have made a change.
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// The `value` *property* sets the current value.
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// This is a quirk of the DOM; I didn't invent it.
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// Other frameworks gloss this over; I think it's
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// more important to give you access to the browser
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// as it really works.
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//
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// tl;dr: use prop:value for form inputs
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prop:value=name
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/>
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<p>"Name is: " {name}</p>
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}
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}
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/// A list of counters that allows you to add or
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/// remove counters.
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#[component]
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fn DynamicList(
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/// The number of counters to begin with.
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initial_length: usize,
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) -> impl IntoView {
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// This dynamic list will use the <For/> component.
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// <For/> is a keyed list. This means that each row
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// has a defined key. If the key does not change, the row
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// will not be re-rendered. When the list changes, only
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// the minimum number of changes will be made to the DOM.
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fn UncontrolledComponent() -> impl IntoView {
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// import the type for <input>
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use leptos::html::Input;
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// `next_counter_id` will let us generate unique IDs
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// we do this by simply incrementing the ID by one
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// each time we create a counter
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let mut next_counter_id = initial_length;
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let (name, set_name) = signal("Uncontrolled".to_string());
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// we generate an initial list as in <StaticList/>
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// but this time we include the ID along with the signal
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// see NOTE in add_counter below re: ArcRwSignal
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let initial_counters = (0..initial_length)
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.map(|id| (id, ArcRwSignal::new(id + 1)))
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.collect::<Vec<_>>();
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// we'll use a NodeRef to store a reference to the input element
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// this will be filled when the element is created
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let input_element: NodeRef<Input> = NodeRef::new();
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// now we store that initial list in a signal
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// this way, we'll be able to modify the list over time,
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// adding and removing counters, and it will change reactively
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let (counters, set_counters) = signal(initial_counters);
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// fires when the form `submit` event happens
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// this will store the value of the <input> in our signal
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let on_submit = move |ev: SubmitEvent| {
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// stop the page from reloading!
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ev.prevent_default();
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let add_counter = move |_| {
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// create a signal for the new counter
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// we use ArcRwSignal here, instead of RwSignal
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// ArcRwSignal is a reference-counted type, rather than the arena-allocated
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// signal types we've been using so far.
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// When we're creating a collection of signals like this, using ArcRwSignal
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// allows each signal to be deallocated when its row is removed.
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let sig = ArcRwSignal::new(next_counter_id + 1);
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// add this counter to the list of counters
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set_counters.update(move |counters| {
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// since `.update()` gives us `&mut T`
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// we can just use normal Vec methods like `push`
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counters.push((next_counter_id, sig))
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});
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// increment the ID so it's always unique
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next_counter_id += 1;
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// here, we'll extract the value from the input
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let value = input_element
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.get()
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// event handlers can only fire after the view
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// is mounted to the DOM, so the `NodeRef` will be `Some`
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.expect("<input> to exist")
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// `NodeRef` implements `Deref` for the DOM element type
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// this means we can call`HtmlInputElement::value()`
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// to get the current value of the input
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.value();
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set_name.set(value);
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};
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view! {
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<div>
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<button on:click=add_counter>
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"Add Counter"
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</button>
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<ul>
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// The <For/> component is central here
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// This allows for efficient, key list rendering
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<For
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// `each` takes any function that returns an iterator
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// this should usually be a signal or derived signal
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// if it's not reactive, just render a Vec<_> instead of <For/>
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each=move || counters.get()
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// the key should be unique and stable for each row
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// using an index is usually a bad idea, unless your list
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// can only grow, because moving items around inside the list
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// means their indices will change and they will all rerender
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key=|counter| counter.0
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// `children` receives each item from your `each` iterator
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// and returns a view
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children=move |(id, count)| {
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// we can convert our ArcRwSignal to a Copy-able RwSignal
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// for nicer DX when moving it into the view
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let count = RwSignal::from(count);
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view! {
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<li>
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<button
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on:click=move |_| *count.write() += 1
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>
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{count}
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</button>
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<button
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on:click=move |_| {
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set_counters
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.write()
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.retain(|(counter_id, _)| {
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counter_id != &id
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});
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}
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>
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"Remove"
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</button>
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</li>
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}
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}
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<form on:submit=on_submit>
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<input type="text"
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// here, we use the `value` *attribute* to set only
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// the initial value, letting the browser maintain
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// the state after that
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value=name
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// store a reference to this input in `input_element`
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node_ref=input_element
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/>
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</ul>
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</div>
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<input type="submit" value="Submit"/>
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</form>
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<p>"Name is: " {name}</p>
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}
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}
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// This `main` function is the entry point into the app
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// It just mounts our component to the <body>
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// Because we defined it as `fn App`, we can now use it in a
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// template as <App/>
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fn main() {
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leptos::mount::mount_to_body(App)
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}
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