# Apollo Client Cache: Type-level Merge Policy for Nested Objects Not Being Applied

**URL:** <https://community.apollographql.com/t/apollo-client-cache-type-level-merge-policy-for-nested-objects-not-being-applied/8965>\
**Category:** Client SDKs\
**Tags:** client, caching\
**Created:** [April 23, 2025, 5:59pm UTC](https://community.apollographql.com/t/apollo-client-cache-type-level-merge-policy-for-nested-objects-not-being-applied/8965 "2025-04-23T17:59:10Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Ali\_Hashemi](https://sea1.discourse-cdn.com/flex019/user_avatar/community.apollographql.com/ali_hashemi/32/6013_2.png) [@Ali\_Hashemi](https://community.apollographql.com/u/Ali_Hashemi)\
**Post date:** [April 23, 2025, 5:59pm UTC](https://community.apollographql.com/t/apollo-client-cache-type-level-merge-policy-for-nested-objects-not-being-applied/8965/1 "2025-04-23T17:59:10Z")

</div>

I’m having an issue with Apollo Client’s cache where my type-level merge policy for `CustomFieldValue` isn’t being applied when I update a `Entry` that contains it.

## My Setup

**Type Structure:**

```auto
type Entry {
  entryUrn: String!
  customFieldValues: [CustomFieldValue]
  # other fields
}

type CustomFieldValue {
  urn: String!
  # other fields
}

```

**Cache Configuration:**

```auto
const cache = new InMemoryCache({
  typePolicies: {
    CustomFieldValue: {
      keyFields: ['urn'],
      merge: mergeCustomFieldValue // Custom merge function for this type
    },
    Entry: {
      keyFields: ['entryUrn'],
    }
  }
});

```

## The Problem:

When I update an `Entry` (through a mutation or cache write) that contains updated `customFieldValues`, the `mergeCustomFieldValue` function defined in my type policy for `CustomFieldValue` is never called. I expect the type-level merge function to be triggered for each `CustomFieldValue` object in the array, but this isn’t happening.

## Question:

Why isn’t my type-level merge policy for `CustomFieldValue` being triggered when I update an `Entry` containing updated `customFieldValues`? Do I need to add something specific to make nested normalized objects use their type-level merge functions during parent object updates?

---

<div class="post-metadata">

**Author:** ![jerelmiller](https://sea1.discourse-cdn.com/flex019/user_avatar/community.apollographql.com/jerelmiller/32/3314_2.png) [@jerelmiller](https://community.apollographql.com/u/jerelmiller)\
**Post date:** [April 25, 2025, 4:44pm UTC](https://community.apollographql.com/t/apollo-client-cache-type-level-merge-policy-for-nested-objects-not-being-applied/8965/2 "2025-04-25T16:44:49Z")

</div>

Hey @Ali_Hashemi 👋

So unfortunately you’re running into one quirky behavior of the cache. You can think of a type-level merge function as a shortcut for defining merge functions for all fields that return a record of that type, rather than thinking of them as a merge function that runs for any record that is that type. There is a subtle difference here and thats because of how it behaves with arrays. Since your field returns an array type, it cannot match a `__typename` property off of it, so your type-level merge function is never called. You’d instead need to define that merge function on the field that returns the array instead.

Its definitely confusing and we plan to change this in v5. I’m sorry I don’t have a better answer for you, but its just an unfortunate quirk of the implementation of the cache today.