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--- |
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id: useQueries |
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title: useQueries |
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--- |
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The `useQueries` hook can be used to fetch a variable number of queries: |
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```tsx |
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const ids = [1, 2, 3] |
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const results = useQueries({ |
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queries: ids.map((id) => ({ |
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queryKey: ['post', id], |
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queryFn: () => fetchPost(id), |
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staleTime: Infinity, |
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})), |
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}) |
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``` |
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**Options** |
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The `useQueries` hook accepts an options object with a **queries** key whose value is an array with query option objects identical to the [`useQuery` hook](../useQuery.md) (excluding the `queryClient` option - because the `QueryClient` can be passed in on the top level). |
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- `queryClient?: QueryClient` |
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- Use this to provide a custom QueryClient. Otherwise, the one from the nearest context will be used. |
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- `combine?: (result: UseQueriesResults) => TCombinedResult` |
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- Use this to combine the results of the queries into a single value. |
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> Having the same query key more than once in the array of query objects may cause some data to be shared between queries. To avoid this, consider de-duplicating the queries and map the results back to the desired structure. |
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**placeholderData** |
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The `placeholderData` option exists for `useQueries` as well, but it doesn't get information passed from previously rendered Queries like `useQuery` does, because the input to `useQueries` can be a different number of Queries on each render. |
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**Returns** |
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The `useQueries` hook returns an array with all the query results. The order returned is the same as the input order. |
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## Combine |
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If you want to combine `data` (or other Query information) from the results into a single value, you can use the `combine` option. The result will be structurally shared to be as referentially stable as possible. |
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```tsx |
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const ids = [1, 2, 3] |
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const combinedQueries = useQueries({ |
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queries: ids.map((id) => ({ |
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queryKey: ['post', id], |
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queryFn: () => fetchPost(id), |
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})), |
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combine: (results) => { |
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return { |
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data: results.map((result) => result.data), |
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pending: results.some((result) => result.isPending), |
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} |
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}, |
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}) |
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``` |
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In the above example, `combinedQueries` will be an object with a `data` and a `pending` property. Note that all other properties of the Query results will be lost. |
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### Memoization |
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The `combine` function will only re-run if: |
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- the `combine` function itself changed referentially |
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- any of the query results changed |
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This means that an inlined `combine` function, as shown above, will run on every render. To avoid this, you can wrap the `combine` function in `useCallback`, or extract it to a stable function reference if it doesn't have any dependencies. |
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