QueryCache is the storage mechanism for React Query. It stores all the data, meta information and state of queries it contains.
Normally, you will not interact with the QueryCache directly and instead use the
QueryClient for a specific cache.
Its available methods are:
onError?: (error: unknown, query: Query) => void
onSuccess?: (data: unknown, query: Query) => void
onSuccess callbacks on the QueryCache can be used to handle these events on a global level. They are different to
defaultOptions provided to the QueryClient because:
defaultOptionscan be overridden by each Query - the global callbacks will always be called.
defaultOptionscallbacks will be called once for each Observer, while the global callbacks will only be called once per Query.
find is a slightly more advanced synchronous method that can be used to get an existing query instance from the cache. This instance not only contains all the state for the query, but all of the instances, and underlying guts of the query as well. If the query does not exist,
undefined will be returned.
Note: This is not typically needed for most applications, but can come in handy when needing more information about a query in rare scenarios (eg. Looking at the query.state.dataUpdatedAt timestamp to decide whether a query is fresh enough to be used as an initial value)
findAll is even more advanced synchronous method that can be used to get existing query instances from the cache that partially match query key. If queries do not exist, empty array will be returned.
Note: This is not typically needed for most applications, but can come in handy when needing more information about a query in rare scenarios
subscribe method can be used to subscribe to the query cache as a whole and be informed of safe/known updates to the cache like query states changing or queries being updated, added or removed
callback: (query?: Query) => void
queryClient.removeQueries, etc). Out of scope mutations to the cache are not encouraged and will not fire subscription callbacks
querywill be passed as first argument to the callback
unsubscribe: Function => void
clear method can be used to clear the cache entirely and start fresh.