/vueuse-functions

useObservable

Use an RxJS Observable, return a ref, and automatically unsubscribe from it when the component is unmounted.

Usage

import { useObservable } from '@vueuse/rxjs'
import { interval } from 'rxjs'
import { mapTo, scan, startWith } from 'rxjs/operators'

// setup()
const count = useObservable(
  interval(1000).pipe(
    mapTo(1),
    startWith(0),
    scan((total, next) => next + total),
  ),
)

Initial Value

You can provide an initial value that will be used before the Observable emits its first value:

import { useObservable } from '@vueuse/rxjs'
import { interval } from 'rxjs'

const count = useObservable(
  interval(1000),
  { initialValue: 0 },
)
// count.value is 0 until the first emission

Error Handling

If you want to add custom error handling to an Observable that might error, you can supply an optional onError configuration. Without this, RxJS will treat any error in the supplied Observable as an "unhandled error" and it will be thrown in a new call stack and reported to window.onerror (or process.on('error') if you happen to be in Node).

import { useObservable } from '@vueuse/rxjs'
import { interval } from 'rxjs'
import { map } from 'rxjs/operators'

// setup()
const count = useObservable(
  interval(1000).pipe(
    map((n) => {
      if (n === 10)
        throw new Error('oops')

      return n + n
    }),
  ),
  {
    onError: (err) => {
      console.log(err.message) // "oops"
    },
  },
)

Options

Type Declarations

export interface UseObservableOptions<I> {
  onError?: (err: any) => void
  /**
   * The value that should be set if the observable has not emitted.
   */
  initialValue?: I | undefined
}
export declare function useObservable<H, I = undefined>(
  observable: Observable<H>,
  options?: UseObservableOptions<I | undefined>,
): Readonly<Ref<H | I>>