class ApolloClient
The ApolloClient class encapsulates Apollo's core client-side API. It backs all available view-layer integrations (React, iOS, and so on).
The ApolloClient constructor
Constructs an instance of ApolloClient.
The constructor for ApolloClient accepts an ApolloClientOptions object that supports the required and optional fields listed below. These fields make it easy to customize how Apollo works based on your application's needs.
Example constructor call
import { ApolloClient } from 'apollo-client';import { InMemoryCache } from 'apollo-cache-inmemory';import { HttpLink } from 'apollo-link-http';// Instantiate required constructor fieldsconst cache = new InMemoryCache();const link = new HttpLink({uri: 'http://localhost:4000/',});const client = new ApolloClient({// Provide required constructor fieldscache: cache,link: link,// Provide some optional constructor fieldsname: 'react-web-client',version: '1.3',queryDeduplication: false,defaultOptions: {watchQuery: {fetchPolicy: 'cache-and-network',},},});
Required fields
| Name | Description |
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link | Apollo Client uses an Apollo Link instance to serve as its network layer. The vast majority of clients use HTTP and should provide an instance of HttpLink from the apollo-link-http package. For more information, see the Apollo Link documentation. |
cache | Apollo Client uses an Apollo Cache instance to handle its caching strategy. The recommended cache is apollo-cache-inmemory, which exports an { InMemoryCache }. For more information, see Configuring the cache. |
Optional fields
| Name | Description |
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name | A custom name (e.g., iOS) that identifies this particular client among your set of clients. Apollo Server uses this property as part of its Client Awareness feature. |
version | A custom version that identifies the current version of this particular client (e.g., 1.2). Apollo Server uses this property as part of its Client Awareness feature. Note that this version string is not the version of Apollo Client that you are using, but rather any version string that helps you differentiate between versions of your client. |
ssrMode | When using Apollo Client for server-side rendering, set this to true so that React Apollo's getDataFromTree function can work effectively. |
ssrForceFetchDelay | Provide this to specify a time interval (in milliseconds) before Apollo Client force-fetches queries after a server-side render. This value is 0 by default. |
connectToDevTools | Set this to true to allow the Apollo Client Devtools Chrome extension to connect to your application's Apollo Client in production. (This connection is allowed automatically in dev mode.) |
queryDeduplication | Set this to false to force all created queries to be sent to the server, even if a query with completely identical parameters (query, variables, operationName) is already in flight. |
defaultOptions | Provide this object to set application-wide default values for options you can provide to the watchQuery, query, and mutate functions. See below for an example object. |
Example defaultOptions object
const defaultOptions = {watchQuery: {fetchPolicy: 'cache-and-network',errorPolicy: 'ignore',},query: {fetchPolicy: 'network-only',errorPolicy: 'all',},mutate: {errorPolicy: 'all',},};
You can override any default option you specify in this object by providing a different value for the same option in individual function calls.
Note: The <Query /> React component uses Apollo Client's watchQuery function. To set defaultOptions when using the <Query /> component, make sure to set them under the defaultOptions.watchQuery property.
ApolloClient functions
This watches the cache store of the query according to the options specified and returns an ObservableQuery. We can subscribe to this ObservableQuery and receive updated results through a GraphQL observer when the cache store changes.
Note that this method is not an implementation of GraphQL subscriptions. Rather, it uses Apollo's store in order to reactively deliver updates to your query results.
For example, suppose you call watchQuery on a GraphQL query that fetches a person's first and last name and this person has a particular object identifier, provided by dataIdFromObject. Later, a different query fetches that same person's first and last name and the first name has now changed. Then, any observers associated with the results of the first query will be updated with a new result object.
Note that if the cache does not change, the subscriber will not be notified.
See here for a description of store reactivity.
Options
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This resolves a single query according to the options specified and returns a Promise which is either resolved with the resulting data or rejected with an error.
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This resolves a single mutation according to the options specified and returns a Promise which is either resolved with the resulting data or rejected with an error.
It takes options as an object with the following keys and values:
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This subscribes to a graphql subscription according to the options specified and returns an Observable which either emits received data or an error.
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Tries to read some data from the store in the shape of the provided
GraphQL query without making a network request. This method will start at
the root query. To start at a specific id returned by dataIdFromObject
use readFragment.
Arguments
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Tries to read some data from the store in the shape of the provided
GraphQL fragment without making a network request. This method will read a
GraphQL fragment from any arbitrary id that is currently cached, unlike
readQuery which will only read from the root query.
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.
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Writes some data in the shape of the provided GraphQL query directly to
the store. This method will start at the root query. To start at a
specific id returned by dataIdFromObject then use writeFragment.
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Writes some data in the shape of the provided GraphQL fragment directly to
the store. This method will write to a GraphQL fragment from any arbitrary
id that is currently cached, unlike writeQuery which will only write
from the root query.
You must pass in a GraphQL document with a single fragment or a document
with multiple fragments that represent what you are writing. If you pass
in a document with multiple fragments then you must also specify a
fragmentName.
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Resets your entire store by clearing out your cache and then re-executing all of your active queries. This makes it so that you may guarantee that there is no data left in your store from a time before you called this method.
resetStore() is useful when your user just logged out. You’ve removed the
user session, and you now want to make sure that any references to data you
might have fetched while the user session was active is gone.
It is important to remember that resetStore() will refetch any active
queries. This means that any components that might be mounted will execute
their queries again using your network interface. If you do not want to
re-execute any queries then you should make sure to stop watching any
active queries.
Allows callbacks to be registered that are executed when the store is
reset. onResetStore returns an unsubscribe function that can be used
to remove registered callbacks.
Arguments
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Remove all data from the store. Unlike resetStore, clearStore will
not refetch any active queries.
Allows callbacks to be registered that are executed when the store is
cleared. onClearStore returns an unsubscribe function that can be used
to remove registered callbacks.
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Call this method to terminate any active client processes, making it safe
to dispose of this ApolloClient instance.
Refetches all of your active queries.
reFetchObservableQueries() is useful if you want to bring the client back to proper state in case of a network outage
It is important to remember that reFetchObservableQueries() will refetch any active
queries. This means that any components that might be mounted will execute
their queries again using your network interface. If you do not want to
re-execute any queries then you should make sure to stop watching any
active queries.
Takes optional parameter includeStandby which will include queries in standby-mode when refetching.
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ObservableQuery functions
ApolloClient Observables extend the Observables implementation provided by zen-observable. Refer to the zen-observable documentation for additional context and API options.
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Update the variables of this observable query, and fetch the new results.
This method should be preferred over setVariables in most use cases.
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Update the variables of this observable query, and fetch the new results
if they've changed. Most users should prefer refetch instead of
setVariables in order to to be properly notified of results even when
they come from the cache.
Note: the next callback will not fire if the variables have not changed
or if the result is coming from cache.
Note: the promise will return the old results immediately if the variables have not changed.
Note: the promise will return null immediately if the query is not active (there are no subscribers).
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Properties
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The current status of a query’s execution in our system.
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