class InMemoryCache
API reference
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):
1// Query a cached Todo object with id 5
2const { todo } = cache.readQuery({
3 query: gql`
4 query ReadTodo {
5 todo(id: 5) {
6 id
7 text
8 completed
9 }
10 }
11 `,
12});
For usage instructions, see Interacting with cached data: readQuery
.
Accepts the following parameters:
Name / Type |
Description |
---|---|
| Required. Provides configuration options for the query, including the actual query to execute.Supported fields are listed below. |
| If true , readQuery returns optimistic results.The default value is false . |
Options
Name / Type |
Description |
---|---|
| Required. The GraphQL query to execute, created by wrapping a query string in the gql template literal. |
| A map of any GraphQL variable names and values required by query . |
| 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 . |
| ⚠️ Deprecated:
Using If true , result objects read from the cache will be canonized, which means deeply-equal objects will also be === (literally the same object), allowing much more efficient comparison of past/present results.The default value is false . |
Signature
1readQuery<QueryType, TVariables = any>(
2 options: DataProxy.Query<TVariables>,
3 optimistic: boolean = false,
4): QueryType | 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.
1// Create or modify a cached Todo object with id 5
2cache.writeQuery({
3 query: gql`
4 query ReadTodo($id: ID!) {
5 todo(id: $id) {
6 id
7 text
8 completed
9 }
10 }
11 `,
12 data: {
13 todo: {
14 __typename: 'Todo',
15 id: 5,
16 text: 'Buy grapes 🍇',
17 completed: false
18 },
19 },
20 variables: {
21 id: 5
22 }
23});
For usage instructions, see Interacting with cached data: writeQuery
.
Takes an options
object as a parameter. Supported fields of this object are described below.
Options
Name / Type |
Description |
---|---|
| Required. The GraphQL query that defines the shape of the data to write. Created by wrapping a query string in the gql template literal. |
| Required. The data to write to the cache. This object's fields must conform to the shape defined by query . |
| A map of any GraphQL variable names and values required by query . |
| The id of the root object to use with query .The default value is ROOT_QUERY , which is the ID of the root query object.By specifying the ID of another cached object, you can modify arbitrary cached data without conforming to the structure of your schema's supported queries. This enables writeQuery to behave similarly to writeFragment . |
| If true , automatically refresh all active queries that depend on at least one field that's modified by this call. If false , silences the broadcast of cache updates and prevents automatic query refresh.The default value is true . |
| If true , ignore existing cache data when calling merge functions, allowing incoming data to replace existing data, without warnings about data loss.The default value is false . |
Signature
1writeQuery<TData = any, TVariables = any>(
2 options: Cache.WriteQueryOptions<TData, TVariables>,
3): Reference | undefined
updateQuery
Since 3.5
Fetches data from the cache in the shape of a provided GraphQL query, then updates that cached data according to a provided update function.
Returns the updated result or null
if the update failed.
1// Fetches a Todo object with id 5 and flips its `completed` boolean
2cache.updateQuery({ // options object
3 query: gql`
4 query ReadTodo($id: ID!) {
5 todo(id: $id) {
6 id
7 text
8 completed
9 }
10 }
11 `,
12 variables: {
13 id: 5
14 }
15}, (data) => ({ // update function
16 todo: {
17 ...data.todo,
18 completed: !data.todo.completed
19 }
20}));
Takes an options
object and an update function as parameters (both described below).
Options
Name / Type |
Description |
---|---|
| Required. The GraphQL query that defines the shape of the data to fetch. Created by wrapping a query string in the gql template literal. |
| A map of any GraphQL variable names and values required by query . |
| 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 . |
| 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 . |
| 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
1public updateQuery<TData = any, TVariables = any>(
2 options: Cache.UpdateQueryOptions<TData, TVariables>,
3 update: (data: TData | null) => TData | null | void,
4): TData | null
readFragment
Reads data from the cache in the shape of a provided GraphQL fragment:
1const todo = cache.readFragment({
2 id: '5', // The value of the to-do item's unique identifier
3 fragment: gql`
4 fragment MyTodo on Todo {
5 id
6 text
7 completed
8 }
9 `,
10});
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:
Name / Type |
Description |
---|---|
| Required. Provides configuration options, including the actual fragment to use.Supported fields are listed below. |
| If true , readFragment returns optimistic results.The default value is false . |
Options
Name / Type |
Description |
---|---|
| 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 . |
| 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. |
| 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. |
| A map of any GraphQL variable names and values required by fragment . |
| ⚠️ Deprecated:
Using If true , result objects read from the cache will be canonized, which means deeply-equal objects will also be === (literally the same object), allowing much more efficient comparison of past/present results.The default value is false . |
Signature
1readFragment<FragmentType, TVariables = any>(
2 options: DataProxy.Fragment<TVariables>,
3 optimistic: boolean = false,
4): FragmentType | 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.
1client.writeFragment({
2 id: 'Todo:5',
3 fragment: gql`
4 fragment MyTodo on Todo {
5 completed
6 }
7 `,
8 data: {
9 completed: true,
10 },
11});
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
Name / Type |
Description |
---|---|
| 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 . |
| 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. |
| Required. The data to write to the cache. This object's fields must conform to the shape defined by fragment . |
| 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. |
| A map of any GraphQL variable names and values required by fragment . |
| 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 . |
| 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
1writeFragment<TData = any, TVariables = any>(
2 options: Cache.WriteFragmentOptions<TData, TVariables>,
3): Reference | undefined
watchFragment
Since 3.10.0
Watches the cache store of the fragment according to the options specified and returns an Observable
. We can subscribe to this Observable
and receive updated results through an observer when the cache store changes.
You must pass in a GraphQL document with a single fragment or a document with multiple fragments that represent what you are reading. If you pass in a document with multiple fragments then you must also specify a fragmentName
.
Signature
1watchFragment<TFragmentData, TVariables>(
2 options: WatchFragmentOptions<TFragmentData, TVariables>
3): Observable<WatchFragmentResult<TFragmentData>>
Parameters
options
WatchFragmentOptions<TFragmentData, TVariables>
An object of type WatchFragmentOptions
that allows the cache to identify the fragment and optionally specify whether to react to optimistic updates.
Result
Observable<WatchFragmentResult<TFragmentData>>
updateFragment
Since 3.5
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.
1// Fetches a Todo object with id 5 and sets its `completed` boolean to true
2const todo = cache.updateFragment({ // options object
3 id: '5', // The value of the to-do item's unique identifier
4 fragment: gql`
5 fragment MyTodo on Todo {
6 completed
7 }
8 `,
9}, (data) => ({ ...data, completed: true }) // update function
10);
Takes an options
object and an update function as parameters (both described below).
Options
Name / Type |
Description |
---|---|
| 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 . |
| 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. |
| 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. |
| A map of any GraphQL variable names and values required by fragment . |
| 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 . |
| 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
1public updateFragment<TData = any, TVariables = any>(
2 options: Cache.UpdateFragmentOptions<TData, TVariables>,
3 update: (data: TData | null) => TData | null | void,
4): TData | null
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:
Name / Type |
Description |
---|---|
| Required. The cached object (or object reference) to obtain the canonical ID for. |
Signature
1identify(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
Name / Type |
Description |
---|---|
| Required. A map that specifies the modifier function to call for each modified field of the cached object.See Modifier function API below. |
| The ID of the cached object to modify.The default value is ROOT_QUERY (the ID of the root query singleton object). |
| If true , also modifies the optimistically cached values for included fields.The default value is false . |
| 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:
Name / Type |
Description |
---|---|
| The name of the field being modified. |
| The full key for the field used internally, including serialized key arguments. |
| A helper function for reading other fields on the object passed to the modifier function as the first parameter. |
| A helper function that returns true for non-normalized StoreObject s and non-dangling Reference s. This indicates that readField(name, objOrRef) has a chance of working.Useful for filtering dangling references out of lists. |
| A helper function that returns true if a particular object is a reference to a cached entity. |
| A sentinel object that you can return from a modifier function to indicate that the field should be deleted entirely. |
Signature
1modify(options: Cache.ModifyOptions): boolean
gc
Performs garbage collection of unreachable normalized objects in the cache:
1cache.gc();
Returns an array containing the IDs of all objects removed from the cache.
For usage instructions, see cache.gc
.
Signature
1gc()
evict
Either removes a normalized object from the cache or removes a specific field from a normalized object in the cache:
1cache.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
Name / Type |
Description |
---|---|
| 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. |
| The name of the field to remove from the cached object.Omit this option if you are removing the entire object. |
| 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. |
| 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
1evict(options: Cache.EvictOptions): boolean
extract
Returns a serialized representation of the cache's current contents as a NormalizedCacheObject
.
Accepts the following parameters:
Name / Type |
Description |
---|---|
| If true , optimistic data is included in the serialization.The default value is false . |
Signature
1extract(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:
Name / Type |
Description |
---|---|
| Required. The serialization to restore the cache from. |
Signature
1restore(data: NormalizedCacheObject): this
makeVar
Creates a reactive variable with an optional initial value:
1const 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:
Name / Type |
Description |
---|---|
Any | The reactive variable's initial value. |
Signature
1makeVar<T>(value: T): ReactiveVar<T>