yew::html

Trait Component

pub trait Component: Sized + 'static {
    type Message: 'static;
    type Properties: Properties;

    // Required methods
    fn create(ctx: &Context<Self>) -> Self;
    fn view(&self, ctx: &Context<Self>) -> Html;

    // Provided methods
    fn update(&mut self, ctx: &Context<Self>, msg: Self::Message) -> bool { ... }
    fn changed(
        &mut self,
        ctx: &Context<Self>,
        _old_props: &Self::Properties,
    ) -> bool { ... }
    fn rendered(&mut self, ctx: &Context<Self>, first_render: bool) { ... }
    fn prepare_state(&self) -> Option<String> { ... }
    fn destroy(&mut self, ctx: &Context<Self>) { ... }
}

Expand description

Components are the basic building blocks of the UI in a Yew app. Each Component chooses how to display itself using received props and self-managed state. Components can be dynamic and interactive by declaring messages that are triggered and handled asynchronously. This async update mechanism is inspired by Elm and the actor model used in the Actix framework.

Required Associated Types§

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type Message: 'static

Messages are used to make Components dynamic and interactive. Simple Component’s can declare their Message type to be (). Complex Component’s commonly use an enum to declare multiple Message types.

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type Properties: Properties

The Component’s properties.

When the parent of a Component is re-rendered, it will either be re-created or receive new properties in the context passed to the changed lifecycle method.

Required Methods§

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fn create(ctx: &Context<Self>) -> Self

Called when component is created.

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fn view(&self, ctx: &Context<Self>) -> Html

Components define their visual layout using a JSX-style syntax through the use of the html! procedural macro. The full guide to using the macro can be found in Yew’s documentation.

Note that view() calls do not always follow a render request from update() or changed(). Yew may optimize some calls out to reduce virtual DOM tree generation overhead. The create() call is always followed by a call to view().

Provided Methods§

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fn update(&mut self, ctx: &Context<Self>, msg: Self::Message) -> bool

Called when a new message is sent to the component via its scope.

Components handle messages in their update method and commonly use this method to update their state and (optionally) re-render themselves.

Returned bool indicates whether to render this Component after update.

By default, this function will return true and thus make the component re-render.

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fn changed( &mut self, ctx: &Context<Self>, _old_props: &Self::Properties, ) -> bool

Called when properties passed to the component change

Returned bool indicates whether to render this Component after changed.

By default, this function will return true and thus make the component re-render.

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fn rendered(&mut self, ctx: &Context<Self>, first_render: bool)

The rendered method is called after each time a Component is rendered but before the browser updates the page.

Note that rendered() calls do not always follow a render request from update() or changed(). Yew may optimize some calls out to reduce virtual DOM tree generation overhead. The create() call is always followed by a call to view() and later rendered().

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