class InMemoryCache

Methods of the InMemoryCache class (the cache used by almost every instance of ApolloClient) are documented here.

Before reading about individual methods, see Caching in Apollo Client.

readQuery

Executes a GraphQL query directly against the cache and returns its result (or null if the query cannot be fulfilled):

// Query a cached Todo object with id 5
const { todo } = cache.readQuery({
  query: gql`
    query ReadTodo {
      todo(id: 5) {
        id
        text
        completed
      }
    }
  `,
});

For usage instructions, see Interacting with cached data: readQuery.

Accepts the following parameters:

options

Object

Required. Provides configuration options for the query, including the actual query to execute.

Supported fields are listed below.

optimistic

Boolean

If true, readQuery returns optimistic results.

The default value is false.

Options

query

DocumentNode

Required. The GraphQL query to execute, created by wrapping a query string in the gql template literal.

variables

Object

A map of any GraphQL variable names and values required by query.

id

String

The root id to use for the query.

The default value is ROOT_QUERY, which is the ID of the root query object.

By specifying the ID of another cached object, you can query arbitrary cached data without conforming to the structure of your schema's supported queries. This enables readQuery to behave similarly to readFragment.

Signature

readQuery<TData = unknown, TVariables = OperationVariables>(
  options: Cache.ReadQueryOptions<TData, TVariables>,
  optimistic: boolean = false,
): Unmasked<TData> | null

writeQuery

Writes data to the cache in the shape of a provided GraphQL query. Returns a Reference to the written object or undefined if the write failed.

// Create or modify a cached Todo object with id 5
cache.writeQuery({
  query: gql`
    query ReadTodo($id: ID!) {
      todo(id: $id) {
        id
        text
        completed
      }
    }
  `,
  data: {
    todo: {
      __typename: "Todo",
      id: 5,
      text: "Buy grapes 🍇",
      completed: false,
    },
  },
  variables: {
    id: 5,
  },
});

For usage instructions, see Interacting with cached data: writeQuery.

Takes an options object as a parameter. Supported fields of this object are described below.

Options

query

DocumentNode

Required. The GraphQL query that defines the shape of the data to write. Created by wrapping a query string in the gql template literal.

data

Object

Required. The data to write to the cache. This object's fields must conform to the shape defined by query.

variables

Object

A map of any GraphQL variable names and values required by query.

id

String

The id of the root object to use with query.

The default value is ROOT_QUERY, which is the ID of the root query object.

By specifying the ID of another cached object, you can modify arbitrary cached data without conforming to the structure of your schema's supported queries. This enables writeQuery to behave similarly to writeFragment.

broadcast

Boolean

If true, automatically refresh all active queries that depend on at least one field that's modified by this call. If false, silences the broadcast of cache updates and prevents automatic query refresh.

The default value is true.

overwrite

Boolean

If true, ignore existing cache data when calling merge functions, allowing incoming data to replace existing data, without warnings about data loss.

The default value is false.

Signature

writeQuery<TData = unknown, TVariables = OperationVariables>(
  options: Cache.WriteQueryOptions<TData, TVariables>,
): Reference | undefined

updateQuery

Fetches data from the cache in the shape of a provided GraphQL query, then updates that cached data according to a provided update function.

Returns the updated result or null if the update failed.

// Fetches a Todo object with id 5 and flips its `completed` boolean
cache.updateQuery(
  // options object
  {
    query: gql`
      query ReadTodo($id: ID!) {
        todo(id: $id) {
          id
          text
          completed
        }
      }
    `,
    variables: {
      id: 5,
    },
  },
  // update function
  (data) => ({
    todo: {
      ...data.todo,
      completed: !data.todo.completed,
    },
  })
);

Takes an options object and an update function as parameters (both described below).

Options

query

DocumentNode

Required. The GraphQL query that defines the shape of the data to fetch. Created by wrapping a query string in the gql template literal.

variables

Object

A map of any GraphQL variable names and values required by query.

id

String

The id of the root object to use with query.

The default value is ROOT_QUERY, which is the ID of the root query object.

By specifying the ID of another cached object, you can modify arbitrary cached data without conforming to the structure of your schema's supported queries. This enables updateQuery to behave similarly to updateFragment.

broadcast

Boolean

If true, automatically refresh all active queries that depend on at least one field that's modified by this call. If false, silences the broadcast of cache updates and prevents automatic query refresh.

The default value is true.

overwrite

Boolean

If true, ignore existing cache data when calling merge functions, allowing incoming data to replace existing data, without warnings about data loss.

The default value is false.

updateQuery update function

The update function of updateQuery takes a query's current cached value and returns the value that should replace it (or undefined if no change should be made).

The returned value is automatically passed to writeQuery, which modifies the cached data.

Please note the update function has to calculate the new value in an immutable way. You can read more about immutable updates in the React documentation.

Signature

public updateQuery<TData = unknown, TVariables = OperationVariables>(
  options: Cache.UpdateQueryOptions<TData, TVariables>,
  update: (data: TData | null) => TData | null | void,
): TData | null

readFragment

Reads data from the cache in the shape of a provided GraphQL fragment:

const todo = cache.readFragment({
  id: "5", // The value of the to-do item's unique identifier
  fragment: gql`
    fragment MyTodo on Todo {
      id
      text
      completed
    }
  `,
});

Returns the requested data or null if data is not available in the cache.

For usage instructions, see Interacting with cached data: readFragment.

Accepts the following parameters:

options

Object

Required. Provides configuration options, including the actual fragment to use.

Supported fields are listed below.

optimistic

Boolean

If true, readFragment returns optimistic results.

The default value is false.

Options

id

String

Required. The ID of the cached object that this call is reading a fragment of.

If the cache does not contain an object with the specified ID, readFragment returns null.

fragment

DocumentNode

Required. A GraphQL document created with the gql template literal tag that includes the fragment to read.

If the document includes more than one fragment, you must also provide fragmentName to indicate which to use.

fragmentName

String

The name of the fragment defined in the fragment document to use in the call.

You don't need to provide this value if the fragment document includes only one fragment.

variables

Object

A map of any GraphQL variable names and values required by fragment.

Signature

readFragment<TData = unknown, TVariables = OperationVariables>(
  options: Cache.ReadFragmentOptions<TData, TVariables>,
  optimistic: boolean = false,
): Unmasked<TData> | null

writeFragment

Writes data to the cache in the shape of the provided GraphQL fragment. Returns a Reference to the written object or undefined if the write failed.

client.writeFragment({
  id: "Todo:5",
  fragment: gql`
    fragment MyTodo on Todo {
      completed
    }
  `,
  data: {
    completed: true,
  },
});

For usage instructions, see Interacting with cached data: writeFragment.

Takes an options object as a parameter. Supported fields of this object are described below.

Options

id

String

Required. The ID of the cached object that this call is writing a fragment to.

If the cache does not contain an object with the specified ID, writeFragment returns null.

fragment

DocumentNode

Required. A GraphQL document created with the gql template literal tag that includes the fragment to write.

If the document includes more than one fragment, you must also provide fragmentName to indicate which to use.

data

Object

Required. The data to write to the cache. This object's fields must conform to the shape defined by fragment.

fragmentName

String

The name of the fragment defined in the fragment document to use in the call.

You don't need to provide this value if the fragment document includes only one fragment.

variables

Object

A map of any GraphQL variable names and values required by fragment.

broadcast

Boolean

If true, automatically refresh all active queries that depend on at least one field that's modified by this call. If false, silences the broadcast of cache updates and prevents automatic query refresh.

The default value is true.

overwrite

Boolean

If true, ignore existing cache data when calling merge functions, allowing incoming data to replace existing data, without warnings about data loss.

The default value is false.

Signature

writeFragment<TData = unknown, TVariables = OperationVariables>(
  options: Cache.WriteFragmentOptions<TData, TVariables>,
): Reference | undefined

<FunctionDetails canonicalReference="@apollo/client!ApolloClient#watchFragment:member(1)" headingLevel={2} />

updateFragment

Fetches data from the cache in the shape of a provided GraphQL fragment, then updates that cached data according to a provided update function.

Returns the updated result or null if the update failed.

// Fetches a Todo object with id 5 and sets its `completed` boolean to true
const todo = cache.updateFragment(
  // options object
  {
    id: "5", // The value of the to-do item's unique identifier
    fragment: gql`
      fragment MyTodo on Todo {
        completed
      }
    `,
  },
  // update function
  (data) => ({ ...data, completed: true })
);

Takes an options object and an update function as parameters (both described below).

Options

id

String

Required. The ID of the cached object that this call is reading a fragment of.

If the cache does not contain an object with the specified ID, updateFragment returns null.

fragment

DocumentNode

Required. A GraphQL document created with the gql template literal tag that includes the fragment to read.

If the document includes more than one fragment, you must also provide fragmentName to indicate which to use.

fragmentName

String

The name of the fragment defined in the fragment document to use in the call.

You don't need to provide this value if the fragment document includes only one fragment.

variables

Object

A map of any GraphQL variable names and values required by fragment.

broadcast

Boolean

If true, automatically refresh all active queries that depend on at least one field that's modified by this call. If false, silences the broadcast of cache updates and prevents automatic query refresh.

The default value is true.

overwrite

Boolean

If true, ignore existing cache data when calling merge functions, allowing incoming data to replace existing data, without warnings about data loss.

The default value is false.

updateFragment update function

The update function of updateFragment takes a fragment's current cached value and returns the value that should replace it (or undefined if no change should be made).

The returned value is automatically passed to writeFragment, which modifies the cached data.

Please note the update function has to calculate the new value in an immutable way. You can read more about immutable updates in the React documentation.

Signature

public updateFragment<TData = unknown, TVariables = OperationVariables>(
  options: Cache.UpdateFragmentOptions<TData, TVariables>,
  update: (data: TData | null) => TData | null | void,
): TData | null

<FunctionDetails canonicalReference="@apollo/client!InMemoryCache#batch:member(1)" headingLevel={2} result={false} />

identify

Returns the canonical ID for a specified cached object.

You can provide either an object or an object reference to this function:

• If you provide an object, identify returns the object's string-based ID (e.g., Car:1).
• If you provide a reference, identify return the reference's __ref ID string.

For usage instructions, see Interacting with cached data: Identify cached entities.

Accepts the following parameters:

object

StoreObject or Reference

Required. The cached object (or object reference) to obtain the canonical ID for.

Signature

identify(object: StoreObject | Reference): string | undefined

modify

Modifies one or more field values of a cached object. Must provide a modifier function for each field to modify. A modifier function takes a cached field's current value and returns the value that should replace it.

Returns true if the cache was modified successfully and false otherwise.

For usage instructions, see Using cache.modify.

Takes an options object as a parameter. Supported fields of this object are described below.

Options

fields

Object

Required. A map that specifies the modifier function to call for each modified field of the cached object.

See Modifier function API below.

id

string

The ID of the cached object to modify.

The default value is ROOT_QUERY (the ID of the root query singleton object).

optimistic

Boolean

If true, also modifies the optimistically cached values for included fields.

The default value is false.

broadcast

Boolean

If true, automatically refresh all active queries that depend on at least one field that's modified by this call. If false, silences the broadcast of cache updates and prevents automatic query refresh.

The default value is true.

Modifier function API

A modifier function takes a cached field's current value and returns the value that should replace it, or the DELETE sentinel object to delete the field entirely.

The first parameter passed to a modifier function is the current cached value of the field being modified.

The second parameter is a helper object that contains the following utilities:

fieldName

String

The name of the field being modified.

storeFieldName

String

The full key for the field used internally, including serialized key arguments.

readField

Function

A helper function for reading other fields on the object passed to the modifier function as the first parameter.

canRead

Function

A helper function that returns true for non-normalized StoreObjects and non-dangling References. This indicates that readField(name, objOrRef) has a chance of working.

Useful for filtering dangling references out of lists.

isReference

Function

A helper function that returns true if a particular object is a reference to a cached entity.

DELETE

Object

A sentinel object that you can return from a modifier function to indicate that the field should be deleted entirely.

Signature

modify(options: Cache.ModifyOptions): boolean

gc

Performs garbage collection of unreachable normalized objects in the cache:

cache.gc();

Returns an array containing the IDs of all objects removed from the cache.

For usage instructions, see cache.gc.

Signature

gc();

evict

Either removes a normalized object from the cache or removes a specific field from a normalized object in the cache:

cache.evict({ id: "my-object-id", fieldName: "myFieldName" });

Returns true if data was removed from the cache, false otherwise.

For usage instructions, see cache.evict.

Takes an options object as a parameter. Supported fields of this object are described below.

Options

id

String

The ID of the cached object to remove (or remove a field from).

The default value is ROOT_QUERY, which is the ID of the root query object.

fieldName

String

The name of the field to remove from the cached object.

Omit this option if you are removing the entire object.

args

Record<string, any>

If provided with fieldName, only instances of the field with the specified arguments are removed from the cache.

Otherwise, all instances of the field are removed for the cached object.

broadcast

Boolean

If true, automatically refresh all active queries that depend on at least one field that's removed by this call. If false, silences the broadcast of cache updates and prevents automatic query refresh.

The default value is true.

Signature

evict(options: Cache.EvictOptions): boolean

extract

Returns a serialized representation of the cache's current contents as a NormalizedCacheObject.

Accepts the following parameters:

optimistic

Boolean

If true, optimistic data is included in the serialization.

The default value is false.

Signature

extract(optimistic: boolean = false): NormalizedCacheObject

restore

Restores the cache's state from a serialized NormalizedCacheObject (such as one returned by extract). This removes all existing data from the cache.

Returns the InMemoryCache instance it's called on.

Accepts the following parameters:

data

NormalizedCacheObject

Required. The serialization to restore the cache from.

Signature

restore(data: NormalizedCacheObject): this

makeVar

Creates a reactive variable with an optional initial value:

const cartItems = makeVar([]);

Returns the reactive variable function you use to read or modify the variable's value.

For usage instructions, see Reactive variables.

Accepts the following parameters:

value

Any

The reactive variable's initial value.

Signature

makeVar<T>(value: T): ReactiveVar<T>