cargo leptos 0.5.0-rc1
v0.5.0-rc1
on Rust Cargo

latest releases: 0.7.0-preview2, 0.7.0-preview, 0.6.11...
12 months ago

I'm planning on releasing 0.5.0 proper toward the end of this week. However, we've continued having some really good new features and some changes, so I want to give it some additional time for testing rather than rushing and breaking things.

For overall 0.5.0 changes, see here.

New Features in this Release

attr: on components, and spreading attributes

Makes it much easier to pass some set of attributes to be given to a component (with attr: passed into a #[prop(attrs)] prop), and then to spread them onto an element with {..attrs} syntax. 

#[component]
pub fn App() -> impl IntoView {
    view! {
        <Input attr:value="hello" attr:label="foo" />
        <Input attr:type="number" attr:value="0" />
    }
}

#[component]
pub fn Input(
    #[prop(attrs)] attrs: Vec<(&'static str, Attribute)>,
) -> impl IntoView {
    view! {
        <input {..attrs} />
        <pre>{format!("{attrs2:#?}")}</pre>
    }
}

Generics on components in view

Newly added support for syntax that identifies a generic type for a component in the view 

#[component]
pub fn GenericComponent<S>(ty: PhantomData<S>) -> impl IntoView {
    std::any::type_name::<S>()
}

#[component]
pub fn App() -> impl IntoView {
    view! {
        <GenericComponent<String> ty=PhantomData />
        <GenericComponent<usize> ty=PhantomData/>
        <GenericComponent<i32> ty=PhantomData/>
    }
}

Callback types

These make it easier to add things like optional callback functions to components. 

#[component]
pub fn App() -> impl IntoView {
    view! {
        <ShowOptFall when=|| { 5 < 3 } fallback=|_| view! { <p>"YES"</p> }>
            <p>"NO"</p>
        </ShowOptFall>
        <ShowOptFall when=|| { 5 < 3 }>
            <p>"NO"</p>
        </ShowOptFall>
        <ShowOptFall when=||{ 5 > 3 }>
            <p>"YES"</p>
        </ShowOptFall>
    }
}

#[component]
pub fn ShowOptFall<W>(
    /// The components Show wraps
    children: Box<dyn Fn() -> Fragment>,
    /// A closure that returns a bool that determines whether this thing runs
    when: W,
    /// A closure that returns what gets rendered if the when statement is false
    #[prop(optional, into)]
    fallback: Option<ViewCallback<()>>,
) -> impl IntoView
where
    W: Fn() -> bool + 'static,
{
    let memoized_when = create_memo(move |_| when());

    move || match memoized_when.get() {
        true => children().into_view(),
        false => match fallback.as_ref() {
            Some(fallback) => fallback.call(()).into_view(),
            None => ().into_view(),
        },
    }
}

with!() and update!() macros

Nested .withI() calls are a pain. Now you can do 

let (first, _) = create_signal("Bob".to_string());
let (middle, _) = create_signal("J.".to_string());
let (last, _) = create_signal("Smith".to_string());
let name = move || with!(|first, middle, last| format!("{first} {middle} {last}"));

instead of 

let name = move || {
	first.with(|first| {
		middle.with(|middle| last.with(|last| format!("{first} {middle} {last}")))
	})
};

Rustier interfaces for signal types

This framework's origins as a Rust port of SolidJS mean we've inherited some functional-JS-isms. Combined with the need to pass cx everywhere prior to 0.5 this has tended to mean we've gone with create_ and so on rather than Rusty ::new(). This simply adds a few Rustier constructors like 

let count = RwSignal::new(0);
let double_count = Memo::new(move |_| count() * 2);

Breaking Changes

  • Renaming .derived_signal() and .mapped_signal_setter() to the more idiomatic .into_signal() and .into_signal_setter()
  • Memoizing whether Suspense is ready yet or not in order to avoid over-re-rendering. Shouldn't break your app, but if something weird happens let me know.
  • Changes timing of create_effect so that it runs a tick after it is created, which solves a number of timing issues with effects that had previously led to create_effect(move || request_animation_frame(move || /* */))

What's Changed

New Contributors

Full Changelog: v0.5.0-beta...v0.5.0-rc1

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