QueryObserver | TanStack Query 简体中文

Defined in: packages/query-core/src/queryObserver.ts:56

A QueryObserver watches a single query in the QueryCache and computes a QueryObserverResult from its state, recomputing and notifying subscribers whenever the underlying query (or the observer's options) changes. It is the primitive that framework adapters (e.g. useQuery) build their hooks on top of, but it can also be used directly to observe and switch between queries outside of any framework.

Example

const observer = new QueryObserver(queryClient, {
  queryKey: ['posts'],
  queryFn: fetchPosts,
})

const unsubscribe = observer.subscribe((result) => {
  console.log(result.data)
})

Extends

Subscribable<QueryObserverListener<TData, TError>>

Extended by

InfiniteQueryObserver

Type Parameters

TQueryFnData

TQueryFnData = unknown

TError

TError = DefaultError

TData

TData = TQueryFnData

TQueryData

TQueryData = TQueryFnData

TQueryKey

TQueryKey extends QueryKey = QueryKey

Constructors

Constructor

new QueryObserver<TQueryFnData, TError, TData, TQueryData, TQueryKey>(client: QueryClient, options: QueryObserverOptions<TQueryFnData, TError, TData, TQueryData, TQueryKey>): QueryObserver<TQueryFnData, TError, TData, TQueryData, TQueryKey>;

Defined in: packages/query-core/src/queryObserver.ts:86

Parameters

client

QueryClient

options

QueryObserverOptions<TQueryFnData, TError, TData, TQueryData, TQueryKey>

Returns

QueryObserver<TQueryFnData, TError, TData, TQueryData, TQueryKey>

Overrides

Subscribable<QueryObserverListener<TData, TError>>.constructor

Properties

options

options: QueryObserverOptions<TQueryFnData, TError, TData, TQueryData, TQueryKey>;

Defined in: packages/query-core/src/queryObserver.ts:88

Methods

destroy()

destroy(): void;

Defined in: packages/query-core/src/queryObserver.ts:166

Stops observing the current query: clears all listeners, cancels the stale and refetch-interval timers, and removes this observer from the query it was observing.

Returns

void

fetchOptimistic()

fetchOptimistic(options: QueryObserverOptions<TQueryFnData, TError, TData, TQueryData, TQueryKey>): Promise<QueryObserverResult<TData, TError>>;

Defined in: packages/query-core/src/queryObserver.ts:412

Fetches a query defined by the given options without affecting this observer's own tracked query or result, and returns a promise that resolves with the QueryObserverResult for that fetch. This is useful for prefetching data that another observer (e.g. a query about to be navigated to) will need, ahead of time.

Parameters

options

QueryObserverOptions<TQueryFnData, TError, TData, TQueryData, TQueryKey>

The observer options of the query to fetch.

Returns

Promise<QueryObserverResult<TData, TError>>

A promise that resolves with the result for the fetched query.

Example

const result = await observer.fetchOptimistic({
  queryKey: ['posts', 2],
  queryFn: () => fetchPost(2),
})
console.log(result.data)

getCurrentQuery()

getCurrentQuery(): Query<TQueryFnData, TError, TQueryData, TQueryKey>;

Defined in: packages/query-core/src/queryObserver.ts:371

Returns the Query instance this observer is currently observing.

Returns

Query<TQueryFnData, TError, TQueryData, TQueryKey>

The observed query.

getCurrentResult()

getCurrentResult(): QueryObserverResult<TData, TError>;

Defined in: packages/query-core/src/queryObserver.ts:330

Returns the most recently computed QueryObserverResult for the observed query. This is a point-in-time read; to be notified of updates as they happen, subscribe to the observer instead (its inherited subscribe method).

Returns

QueryObserverResult<TData, TError>

The observer's latest result.

Example

const result = observer.getCurrentResult()
console.log(result.status, result.data)

getOptimisticResult()

getOptimisticResult(options: DefaultedQueryObserverOptions<TQueryFnData, TError, TData, TQueryData, TQueryKey>): QueryObserverResult<TData, TError>;

Defined in: packages/query-core/src/queryObserver.ts:281

Computes the result the observer would produce for the given (already-defaulted) options right now, building the underlying Query if it doesn't exist yet, without waiting for a subscription callback. Called by framework adapters on every render (e.g. useQuery) so the returned value is available synchronously, ahead of setOptions triggering an actual fetch.

Parameters

options

DefaultedQueryObserverOptions<TQueryFnData, TError, TData, TQueryData, TQueryKey>

The defaulted observer options to compute the result for.

Returns

QueryObserverResult<TData, TError>

The result for the given options.

hasListeners()

hasListeners(): boolean;

Defined in: packages/query-core/src/subscribable.ts:43

Returns true while at least one listener is registered, false once they have all unsubscribed.

Returns

boolean

true if at least one listener is registered.

Inherited from

Subscribable.hasListeners

refetch()

refetch(options?: RefetchOptions): Promise<QueryObserverResult<TData, TError>>;

Defined in: packages/query-core/src/queryObserver.ts:387

Refetches the observed query and returns a promise that resolves with the resulting QueryObserverResult.

Parameters

options?

RefetchOptions = {}

Set cancelRefetch to false to keep a running fetch instead of cancelling it, and throwOnError to true to reject when the refetch fails.

Returns

Promise<QueryObserverResult<TData, TError>>

A promise that resolves with the result after the refetch.

Example

const result = await observer.refetch({ cancelRefetch: false })
console.log(result.data)

setOptions()

setOptions(options: QueryObserverOptions<TQueryFnData, TError, TData, TQueryData, TQueryKey>): void;

Defined in: packages/query-core/src/queryObserver.ts:189

Updates the observer's options. This will re-resolve the query being observed (switching to a different query if the queryKey changed), trigger a fetch if the new options require one and the observer has subscribers, recompute the current result, and reschedule the stale and refetch-interval timers as needed.

Parameters

options

QueryObserverOptions<TQueryFnData, TError, TData, TQueryData, TQueryKey>

The new observer options. They are defaulted with QueryClient#defaultQueryOptions before being applied.

Returns

void

Throws

If enabled is neither a boolean nor a function.

Example

observer.setOptions({ queryKey: ['posts', 1], queryFn: () => fetchPost(1) })
// later: switch to a different query, reusing the same observer
observer.setOptions({ queryKey: ['posts', 2], queryFn: () => fetchPost(2) })

shouldFetchOnReconnect()

shouldFetchOnReconnect(): boolean;

Defined in: packages/query-core/src/queryObserver.ts:139

Returns whether the observed query is currently stale and configured (via the refetchOnReconnect option) to refetch when the network reconnects.

Returns

boolean

true if the observer should refetch the query on reconnect.

shouldFetchOnWindowFocus()

shouldFetchOnWindowFocus(): boolean;

Defined in: packages/query-core/src/queryObserver.ts:153

Returns whether the observed query is currently stale and configured (via the refetchOnWindowFocus option) to refetch when the window regains focus.

Returns

boolean

true if the observer should refetch the query on window focus.

subscribe(listener: QueryObserverListener): () => void;

Defined in: packages/query-core/src/subscribable.ts:28

Registers a listener to be called on every update this object notifies about. Returns a function that removes the listener again — call it to stop listening. The base class never drops a listener on its own, though some subclasses clear all of theirs in destroy().

Parameters

listener

QueryObserverListener

Called on each update, with whatever the subclass passes to its subscribers.

Returns

A function that removes the listener.

() => void

Example

const unsubscribe = subscribable.subscribe(() => {
  // react to the update
})

unsubscribe()

Inherited from

Subscribable.subscribe

trackProp()

trackProp(key: 
  | "error"
  | "data"
  | "isError"
  | "isPending"
  | "isLoading"
  | "isLoadingError"
  | "isRefetchError"
  | "isSuccess"
  | "isPlaceholderData"
  | "status"
  | "dataUpdatedAt"
  | "errorUpdatedAt"
  | "failureCount"
  | "failureReason"
  | "errorUpdateCount"
  | "isFetched"
  | "isFetchedAfterMount"
  | "isFetching"
  | "isInitialLoading"
  | "isPaused"
  | "isRefetching"
  | "isStale"
  | "isEnabled"
  | "refetch"
  | "fetchStatus"): void;

Defined in: packages/query-core/src/queryObserver.ts:363

Records that the given QueryObserverResult property was read, so a subsequent update only notifies this observer if a tracked property actually changed. Normally called indirectly via QueryObserver#trackResult's proxy; exposed directly for adapters that track property access themselves (e.g. through their own reactivity system) instead of via the proxy.

Parameters

key

The name of the property that was read.

Returns

void

trackResult()

trackResult(result: QueryObserverResult<TData, TError>, onPropTracked?: (key: 
  | "error"
  | "data"
  | "isError"
  | "isPending"
  | "isLoading"
  | "isLoadingError"
  | "isRefetchError"
  | "isSuccess"
  | "isPlaceholderData"
  | "status"
  | "dataUpdatedAt"
  | "errorUpdatedAt"
  | "failureCount"
  | "failureReason"
  | "errorUpdateCount"
  | "isFetched"
  | "isFetchedAfterMount"
  | "isFetching"
  | "isInitialLoading"
  | "isPaused"
  | "isRefetching"
  | "isStale"
  | "isEnabled"
  | "refetch"
| "fetchStatus") => void): QueryObserverResult<TData, TError>;

Defined in: packages/query-core/src/queryObserver.ts:343

Wraps a QueryObserverResult in a Proxy that records which properties are read, via QueryObserver#trackProp (and an optional onPropTracked callback). Used by framework adapters when notifyOnChangeProps is not set, to implement its default "only re-render on properties you actually read" behavior.

Parameters

result

QueryObserverResult<TData, TError>

The result to wrap.

onPropTracked?

Called with the name of each property that is read.

Returns

QueryObserverResult<TData, TError>

A proxy of result that tracks property reads.

updateResult()

updateResult(): void;

Defined in: packages/query-core/src/queryObserver.ts:765

Recomputes and stores the current result from the current query/options, notifying listeners if it changed. Framework adapters call this right after subscribing to make sure no query update was missed in the gap between creating the observer and subscribing to it.

Returns

void