bind(observable)

Binds an Observable to React, and returns a hook and shared stream representing the source Observable.

function bind<T>(
observable: Observable<T>,
defaultValue?: T,
) {
const state$ = state(observable, defaultValue);
return [
() => useStateObservable(state$),
state$
];
}

Arguments

  • observable: The source Observable to be used by the hook.
  • defaultValue: (Optional) value to return when the source hasn't emitted yet.

Returns

[1, 2]:

  1. A React Hook that yields the latest emitted value of the Observable. If the Observable doesn't synchronously emit a value, it will return the defaultValue if provided, otherwise it will leverage React Suspense while it's waiting for the first value. It's equivalent to useStateObservable of the resulting StateObservable.

  2. The StateObservable that the hook uses: It also replays back the latest value emitted. It can be used for composing other streams that depend on it.

note

bind doesn't propagate completions from the source stream - the shared subscription is closed as soon as there are no subscribers to that Observable.

Example

import { scan } from "rxjs/operators"
import { bind } from "@react-rxjs/core"
const [useCounter, counter$] = bind(
clicks$.pipe(scan((prev) => prev + 1, 0)),
0,
)
function CounterDisplay() {
const counter = useCounter()
return <div>{counter}</div>
}

Factory Overload

Binds an Observable factory function to React, and returns a hook and shared stream representing the created Observables.

function bind<A extends unknown[], O>(
getObservable: (...args: A) => Observable<O>,
defaultValue?: (...args: A) => T | T,
) {
const state$ = state(getObservable, defaultValue);
return [
(...args: A) => useStateObservable(state$(...args)),
state$
];
}

Arguments

  • getObservable: Factory of Observables. The arguments of this function will be the ones used in the hook.

Returns

[1, 2]:

  1. A React hook with the same arguments as the factory function. This hook will yield the latest update from the Observable returned from the factory function. If the Observable doesn't synchronously emit a value, it will return the defaultValue if provided, otherwise it will leverage React Suspense while it's waiting for the first value. It's equivalent to useStateObservable of the resulting StateObservable.

  2. The factory function that returns the StateObservable that the hook uses for the specific arguments. It can be used for composing other streams that depend on it.

Example

const [useStory, getStory$] = bind((storyId: number) =>
getStoryWithUpdates$(storyId),
)
const Story: React.FC<{ id: number }> = ({ id }) => {
const story = useStory(id)
return (
<article>
<h1>{story.title}</h1>
<p>{story.description}</p>
</article>
)
}

See also