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Add comprehensive reference documentation for: - Vitest: environments, projects/workspaces, type testing, vi utilities - Pinia: HMR, Nuxt integration, SSR setup - Vue: built-in components (Transition, Teleport, Suspense, KeepAlive) and advanced directives
78 lines
2.0 KiB
Markdown
78 lines
2.0 KiB
Markdown
---
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category: '@RxJS'
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---
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# useSubject
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Bind an RxJS [`Subject`](https://rxjs.dev/guide/subject) to a `ref` and propagate value changes both ways.
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## Usage
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<!-- TODO: import rxjs error if enable twoslash -->
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```ts no-twoslash
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import { useSubject } from '@vueuse/rxjs'
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import { Subject } from 'rxjs'
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const subject = new Subject()
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// setup()
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const subjectRef = useSubject(subject)
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// Changes to subjectRef.value will be pushed to the subject
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subjectRef.value = 'new value'
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// Values emitted by the subject will update subjectRef
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subject.next('from subject')
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```
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### With BehaviorSubject
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When using a `BehaviorSubject`, the returned ref is initialized with the subject's current value and the type does not include `undefined`:
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```ts no-twoslash
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import { useSubject } from '@vueuse/rxjs'
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import { BehaviorSubject } from 'rxjs'
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const subject = new BehaviorSubject('initial')
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// setup()
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const subjectRef = useSubject(subject) // Ref<string>, not Ref<string | undefined>
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console.log(subjectRef.value) // 'initial'
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```
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### Error Handling
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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).
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```ts no-twoslash
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import { useSubject } from '@vueuse/rxjs'
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import { Subject } from 'rxjs'
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const subject = new Subject()
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// setup()
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const subjectRef = useSubject(subject, {
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onError: (err) => {
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console.log(err.message) // "oops"
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},
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},)
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```
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## Type Declarations
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```ts
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export interface UseSubjectOptions<I = undefined> extends Omit<
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UseObservableOptions<I>,
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"initialValue"
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> {}
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export declare function useSubject<H>(
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subject: BehaviorSubject<H>,
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options?: UseSubjectOptions,
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): Ref<H>
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export declare function useSubject<H>(
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subject: Subject<H>,
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options?: UseSubjectOptions,
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): Ref<H | undefined>
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```
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