Updating the cache using data classes is tedious

[teodorpenkov]

Background We are doing pagination via the apollo cache - The flow is basically watching an initial query for the first page and update the cache when more data is available. That way we have only 1 watcher per pageable component.

The cache update is rather tedious tho e.g. :

data.copy(
  account = data.account.copy(
    inbox = data.account.inbox.copy(
      fragments = data.account.inbox.fragments.copy(
        receiptPage = data.account.inbox.fragments.receiptPage.copy(
          nodes = listOf(node) + data.account.inbox.fragments.receiptPage.nodes,
          pageInfo = data.account.inbox.fragments.receiptPage.pageInfo
        )
      )
    )
  )
)

In the above example everything except nodes and pageInfo is unchanged. In the Swift version we can directly update them (value types 😏)

Question.

What would you recommend to do in this case? I know there are libraries like arrow which can simplify the problem but the integration with the apollo coden will be really tricky.

[BoD]

Hi! 👋 Thanks for the question!

As of today we don't really have a satisfying answer to this. Improving the story of using pagination with caching in particular is on our roadmap, as we know this use-case is important to a lot of users.

One thing you could do to simplify the code a bit is to update a fragment in the cache instead of the whole data, something like:

val id = "QUERY_ROOT.account.inbox" // Or any other id you defined
val variables = Variables.EMPTY_VARIABLES // Or the variables used
write(fragment, CacheKey(id), variables)

We didn't know Arrow could be a potential candidate or path for this so thanks for the pointer! If you have any other ideas or feedback on this area please don't hesitate to share.

[teodorpenkov]

Thanks for answering. I'm trying to make arrow work with the current state of the library. I basically need to write a kotlin compiler plugin that will generate the code that arrow generates when the apollo codegen is finished. I will let you know if I have something working in this issue.

[BoD]

Interesting! Yes, don't hesitate to share your findings.

[martinbonnin]

Linking this forum post here since it's the same issue: https://spectrum.chat/apollo/apollo-android/update-cache-using-previous-query-data-ios-parallel~bd005192-cbf7-440b-9482-8adb028e283d