| --- |
| id: MutationCache |
| title: MutationCache |
| --- |
| |
| The `MutationCache` is the storage for mutations. |
|
|
| **Normally, you will not interact with the MutationCache directly and instead use the `QueryClient`.** |
|
|
| ```tsx |
| import { MutationCache } from '@tanstack/react-query' |
| |
| const mutationCache = new MutationCache({ |
| onError: (error) => { |
| console.log(error) |
| }, |
| onSuccess: (data) => { |
| console.log(data) |
| }, |
| }) |
| ``` |
|
|
| Its available methods are: |
|
|
| - [`getAll`](#mutationcachegetall) |
| - [`subscribe`](#mutationcachesubscribe) |
| - [`clear`](#mutationcacheclear) |
|
|
| **Options** |
|
|
| - `onError?: (error: unknown, variables: unknown, context: unknown, mutation: Mutation) => Promise<unknown> | unknown` |
| - Optional |
| - This function will be called if some mutation encounters an error. |
| - If you return a Promise from it, it will be awaited |
| - `onSuccess?: (data: unknown, variables: unknown, context: unknown, mutation: Mutation) => Promise<unknown> | unknown` |
| - Optional |
| - This function will be called if some mutation is successful. |
| - If you return a Promise from it, it will be awaited |
| - `onSettled?: (data: unknown | undefined, error: unknown | null, variables: unknown, context: unknown, mutation: Mutation) => Promise<unknown> | unknown` |
| - Optional |
| - This function will be called if some mutation is settled (either successful or errored). |
| - If you return a Promise from it, it will be awaited |
| - `onMutate?: (variables: unknown, mutation: Mutation) => Promise<unknown> | unknown` |
| - Optional |
| - This function will be called before some mutation executes. |
| - If you return a Promise from it, it will be awaited |
|
|
| ## Global callbacks |
|
|
| The `onError`, `onSuccess`, `onSettled` and `onMutate` callbacks on the MutationCache can be used to handle these events on a global level. They are different to `defaultOptions` provided to the QueryClient because: |
|
|
| - `defaultOptions` can be overridden by each Mutation - the global callbacks will **always** be called. |
| - `onMutate` does not allow returning a context value. |
|
|
| ## `mutationCache.getAll` |
|
|
| `getAll` returns all mutations within the cache. |
|
|
| > Note: This is not typically needed for most applications, but can come in handy when needing more information about a mutation in rare scenarios |
|
|
| ```tsx |
| const mutations = mutationCache.getAll() |
| ``` |
|
|
| **Returns** |
|
|
| - `Mutation[]` |
| - Mutation instances from the cache |
|
|
| ## `mutationCache.subscribe` |
|
|
| The `subscribe` method can be used to subscribe to the mutation cache as a whole and be informed of safe/known updates to the cache like mutation states changing or mutations being updated, added or removed. |
|
|
| ```tsx |
| const callback = (event) => { |
| console.log(event.type, event.mutation) |
| } |
| |
| const unsubscribe = mutationCache.subscribe(callback) |
| ``` |
|
|
| **Options** |
|
|
| - `callback: (mutation?: MutationCacheNotifyEvent) => void` |
| - This function will be called with the mutation cache any time it is updated. |
|
|
| **Returns** |
|
|
| - `unsubscribe: Function => void` |
| - This function will unsubscribe the callback from the mutation cache. |
|
|
| ## `mutationCache.clear` |
|
|
| The `clear` method can be used to clear the cache entirely and start fresh. |
|
|
| ```tsx |
| mutationCache.clear() |
| ``` |
|
|
