Advanced Reactivity

Contexts

Contexts provide an easy way to share data between components without drilling props through multiple levels of the component hierarchy.

Creating a ContextProvider is required before any components can use the context. The value used should implement Clone.

Using ContextProvider

ContextProvider is a component like any other. It takes a value prop which is the context value and a children prop which is the child components that have access to the context value.

Using use_context

use_context returns a clone of the value for a context of a given type.

Example

use sycamore::prelude::*;
use sycamore::rx::{ContextProvider, ContextProviderProps, use_context};

struct Counter(Signal<i32>);

#[component(CounterView)]
fn counter_view() -> Template<G> {
    let counter = use_context::<Counter>();

    template! {
        (counter.0.get())
    }
}

template! {
    ContextProvider(ContextProviderProps {
        value: Counter(Signal::new(0)),
        children: || template! {
            CounterView()
        }
    })
}

Remember that unlike contexts in React and many other libraries, the value prop is not reactive by itself. This is because components only run once. In order to make a context value reactive, you need to use a Signal or other reactive data structure.

Reactive scopes

on_cleanup

Nested effects

TODO

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