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ApolloStore


Apollo Kotlin exposes the ApolloStore API to read and write from the normalized cache programmatically. The ApolloStore sits on top of NormalizedCache, exposes a thread safe API as well as methods that make it easier to read and write fragments and operations.

The store is accessible with the ApolloClient.apolloStore extension:

val apolloClient = ApolloClient.Builder()
  .serverUrl("https://...")
  .normalizedCache(MemoryCacheFactory(maxSizeBytes = 10 * 1024 * 1024))
  .build()

val apolloStore: ApolloStore = apolloClient.apolloStore

Reading operation data

Just like a regular GraphQL query, the main way to use the store is to read and write queries:

Given the following query:

query GetBook($id: String!) {
  book(id: $id) {
    title
    author {
      name
    }
  }
}

You can read it like this:

val data = apolloClient.apolloStore.readOperation(GetBookQuery(id = "42"))

println("Title=${data.title}")
println("Author Name=${data.author.name}")

In the event of cache miss, readOperation will throw:

try {
  apolloClient.apolloStore.readOperation(GetBookQuery(id = "42"))
} catch(e: CacheMissException) {
  println("CacheMiss on key: ${e.key}.${e.fieldName}")
}

Writing operation data

Writing operation data is similar to reading:

apolloClient.apolloStore.writeOperation(GetBookQuery(id = "42"), data)

Note how you'll need to pass the data allong the operation.

Reading and Writing fragments

In the GraphQL specification, fragments are always part of a larger operation and cannot be executed standalone.

fragment BookDetails on Book {
  id
  title
  author {
    name
  }
}

Apollo Kotlin makes an exception to that rule and allows to read/write individual fragments. This is disabled by default and can be enabled with generateFragmentImplementations:

apollo {
  generateFragmentImplementations.set(true)
}

Because fragments are not rooted, you need to specify the root cache id of the fragment:

val data = apolloClient.apolloStore.readFragment(BookDetailsImpl(), CacheKey("42")

println("Title=${data.title}")
println("Author Name=${data.author.name}")

Fragments can contain variables. Different fragments with different variables can return different data. In that case the fragment Impl class will require variables as constructor parameters:

fragment BookDetails on Book {
  id
  title(locale: $locale)
}
val data = apolloClient.apolloStore.readFragment(BookDetailsImpl(locale = "en-US"), CacheKey("42")

println("Title=${data.title}")
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