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:

1val apolloClient = ApolloClient.Builder()
2  .serverUrl("https://...")
3  .normalizedCache(MemoryCacheFactory(maxSizeBytes = 10 * 1024 * 1024))
4  .build()
5
6val 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:

1query GetBook($id: String!) {
2  book(id: $id) {
3    title
4    author {
5      name
6    }
7  }
8}

You can read it like this:

1val data = apolloClient.apolloStore.readOperation(GetBookQuery(id = "42"), apolloClient.customScalarAdapters)
2
3println("Title=${data.title}")
4println("Author Name=${data.author.name}")

In the event of cache miss, readOperation will throw:

1try {
2  apolloClient.apolloStore.readOperation(GetBookQuery(id = "42"), apolloClient.customScalarAdapters)
3} catch(e: CacheMissException) {
4  println("CacheMiss on key: ${e.key}.${e.fieldName}")
5}

If you declared scalar adapters at runtime, pass your client's customScalarAdapters to the store's methods, as the store will need them to convert scalar values to and from their Kotlin/Java types.

Writing operation data

Writing operation data is similar to reading:

1apolloClient.apolloStore.writeOperation(GetBookQuery(id = "42"), data, apolloClient.customScalarAdapters)

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.

1fragment BookDetails on Book {
2  id
3  title
4  author {
5    name
6  }
7}

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:

1apollo {
2  service("service") {
3    generateFragmentImplementations.set(true)
4  }
5}

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

1val data = apolloClient.apolloStore.readFragment(BookDetailsImpl(), CacheKey("42"), apolloClient.customScalarAdapters)
2
3println("Title=${data.title}")
4println("Author Name=${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:

1fragment BookDetails on Book {
2  id
3  title(locale: $locale)
4}

1val data = apolloClient.apolloStore.readFragment(BookDetailsImpl(locale = "en-US"), CacheKey("42"), apolloClient.customScalarAdapters)
2
3println("Title=${data.title}")

Clearing the cache

Call apolloClient.apolloStore.clearAll() to clear the cache of all entries.