Function use_context

pub fn use_context<T: Clone + PartialEq + 'static>() -> impl Hook<Output = Option<T>>

Hook for consuming context values in function components. The context of the type passed as T is returned. If there is no such context in scope, None is returned. A component which calls use_context will re-render when the data of the context changes.

More information about contexts and how to define and consume them can be found on Yew Docs.

Example

use yew::{ContextProvider, function_component, html, use_context, use_state, Html};


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

/// Main component
#[function_component]
pub fn App() -> Html {
    let ctx = use_state(|| Theme {
        foreground: "#000000".to_owned(),
        background: "#eeeeee".to_owned(),
    });

    html! {
        // `ctx` is type `Rc<UseStateHandle<Theme>>` while we need `Theme`
        // so we deref it.
        // It derefs to `&Theme`, hence the clone
        <ContextProvider<Theme> context={(*ctx).clone()}>
            // Every child here and their children will have access to this context.
            <Toolbar />
        </ContextProvider<Theme>>
    }
}

/// The toolbar.
/// This component has access to the context
#[function_component]
pub fn Toolbar() -> Html {
    html! {
        <div>
            <ThemedButton />
        </div>
    }
}

/// Button placed in `Toolbar`.
/// As this component is a child of `ThemeContextProvider` in the component tree, it also has access to the context.
#[function_component]
pub fn ThemedButton() -> Html {
    let theme = use_context::<Theme>().expect("no ctx found");

    html! {
        <button style={format!("background: {}; color: {};", theme.background, theme.foreground)}>
            { "Click me!" }
        </button>
    }
}