/vueuse-functions

useSubject

Bind an RxJS Subject to a ref and propagate value changes both ways.

Usage

import { useSubject } from '@vueuse/rxjs'
import { Subject } from 'rxjs'

const subject = new Subject()

// setup()
const subjectRef = useSubject(subject)

// Changes to subjectRef.value will be pushed to the subject
subjectRef.value = 'new value'

// Values emitted by the subject will update subjectRef
subject.next('from subject')

With BehaviorSubject

When using a BehaviorSubject, the returned ref is initialized with the subject's current value and the type does not include undefined:

import { useSubject } from '@vueuse/rxjs'
import { BehaviorSubject } from 'rxjs'

const subject = new BehaviorSubject('initial')

// setup()
const subjectRef = useSubject(subject) // Ref<string>, not Ref<string | undefined>
console.log(subjectRef.value) // 'initial'

Error Handling

If you want to add custom error handling to a Subject 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 { useSubject } from '@vueuse/rxjs'
import { Subject } from 'rxjs'

const subject = new Subject()

// setup()
const subjectRef = useSubject(subject, {
  onError: (err) => {
    console.log(err.message) // "oops"
  },
},)

Type Declarations

export interface UseSubjectOptions<I = undefined> extends Omit<
  UseObservableOptions<I>,
  "initialValue"
> {}
export declare function useSubject<H>(
  subject: BehaviorSubject<H>,
  options?: UseSubjectOptions,
): Ref<H>
export declare function useSubject<H>(
  subject: Subject<H>,
  options?: UseSubjectOptions,
): Ref<H | undefined>