| --- |
| id: hydration |
| title: hydration |
| --- |
| |
| ## `dehydrate` |
|
|
| `dehydrate` creates a frozen representation of a `cache` that can later be hydrated with `HydrationBoundary` or `hydrate`. This is useful for passing prefetched queries from server to client or persisting queries to localStorage or other persistent locations. It only includes currently successful queries by default. |
|
|
| ```tsx |
| import { dehydrate } from '@tanstack/react-query' |
| |
| const dehydratedState = dehydrate(queryClient, { |
| shouldDehydrateQuery, |
| shouldDehydrateMutation, |
| }) |
| ``` |
|
|
| **Options** |
|
|
| - `client: QueryClient` |
| - **Required** |
| - The `queryClient` that should be dehydrated |
| - `options: DehydrateOptions` |
| - Optional |
| - `shouldDehydrateMutation: (mutation: Mutation) => boolean` |
| - Optional |
| - Whether to dehydrate mutations. |
| - The function is called for each mutation in the cache |
| - Return `true` to include this mutation in dehydration, or `false` otherwise |
| - Defaults to only including paused mutations |
| - If you would like to extend the function while retaining the default behavior, import and execute `defaultShouldDehydrateMutation` as part of the return statement |
| - `shouldDehydrateQuery: (query: Query) => boolean` |
| - Optional |
| - Whether to dehydrate queries. |
| - The function is called for each query in the cache |
| - Return `true` to include this query in dehydration, or `false` otherwise |
| - Defaults to only including successful queries |
| - If you would like to extend the function while retaining the default behavior, import and execute `defaultShouldDehydrateQuery` as part of the return statement |
| - `serializeData?: (data: any) => any` A function to transform (serialize) data during dehydration. |
| - `shouldRedactErrors?: (error: unknown) => boolean` |
| - Optional |
| - Whether to redact errors from the server during dehydration. |
| - The function is called for each error in the cache |
| - Return `true` to redact this error, or `false` otherwise |
| - Defaults to redacting all errors |
|
|
| **Returns** |
|
|
| - `dehydratedState: DehydratedState` |
| - This includes everything that is needed to hydrate the `queryClient` at a later point |
| - You **should not** rely on the exact format of this response, it is not part of the public API and can change at any time |
| - This result is not in serialized form, you need to do that yourself if desired |
|
|
| ### Limitations |
|
|
| Some storage systems (such as browser [Web Storage API](https://developer.mozilla.org/en-US/docs/Web/API/Web_Storage_API)) require values to be JSON serializable. If you need to dehydrate values that are not automatically serializable to JSON (like `Error` or `undefined`), you have to serialize them for yourself. Since only successful queries are included per default, to also include `Errors`, you have to provide `shouldDehydrateQuery`, e.g.: |
|
|
| ```tsx |
| // server |
| const state = dehydrate(client, { shouldDehydrateQuery: () => true }) // to also include Errors |
| const serializedState = mySerialize(state) // transform Error instances to objects |
| |
| // client |
| const state = myDeserialize(serializedState) // transform objects back to Error instances |
| hydrate(client, state) |
| ``` |
|
|
| ## `hydrate` |
|
|
| `hydrate` adds a previously dehydrated state into a `cache`. |
|
|
| ```tsx |
| import { hydrate } from '@tanstack/react-query' |
| |
| hydrate(queryClient, dehydratedState, options) |
| ``` |
|
|
| **Options** |
|
|
| - `client: QueryClient` |
| - **Required** |
| - The `queryClient` to hydrate the state into |
| - `dehydratedState: DehydratedState` |
| - **Required** |
| - The state to hydrate into the client |
| - `options: HydrateOptions` |
| - Optional |
| - `defaultOptions: DefaultOptions` |
| - Optional |
| - `mutations: MutationOptions` The default mutation options to use for the hydrated mutations. |
| - `queries: QueryOptions` The default query options to use for the hydrated queries. |
| - `deserializeData?: (data: any) => any` A function to transform (deserialize) data before it is put into the cache. |
| - `queryClient?: QueryClient`, |
| - Use this to use a custom QueryClient. Otherwise, the one from the nearest context will be used. |
|
|
| ### Limitations |
|
|
| If the queries you're trying to hydrate already exist in the queryCache, `hydrate` will only overwrite them if the data is newer than the data present in the cache. Otherwise, it will **not** get applied. |
|
|
| [//]: # 'HydrationBoundary' |
|
|
| ## `HydrationBoundary` |
|
|
| `HydrationBoundary` adds a previously dehydrated state into the `queryClient` that would be returned by `useQueryClient()`. If the client already contains data, the new queries will be intelligently merged based on update timestamp. |
|
|
| ```tsx |
| import { HydrationBoundary } from '@tanstack/react-query' |
| |
| function App() { |
| return <HydrationBoundary state={dehydratedState}>...</HydrationBoundary> |
| } |
| ``` |
|
|
| > Note: Only `queries` can be dehydrated with an `HydrationBoundary`. |
|
|
| **Options** |
|
|
| - `state: DehydratedState` |
| - The state to hydrate |
| - `options: HydrateOptions` |
| - Optional |
| - `defaultOptions: QueryOptions` |
| - The default query options to use for the hydrated queries. |
| - `queryClient?: QueryClient`, |
| - Use this to use a custom QueryClient. Otherwise, the one from the nearest context will be used. |
|
|
| [//]: # 'HydrationBoundary' |
|
|
