Fragments

Apollo Android supports GraphQL fragments. Fragments allow you to define a set of fields that can be reusable in your queries.

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fragment launchFragment on Launch {
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  id
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  site
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  mission {
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    name
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  }
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}
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query LaunchDetails($id:ID!) {
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  launch(id: $id) {
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    ...launchFragment
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  }
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}

Apollo Android will generate a LaunchFragment class that can be reused in different queries:

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data class LaunchFragment(
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     val __typename: String = "Launch",
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     val id: String,
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     val site: String?,
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     val mission: Mission?
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   )

Your generated models will have a .fragments property to access the fragments:

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println("Mission site: ${launch.fragments.launchFragment.site}")

To reuse a fragment, use it in any other query:

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// ...
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query LaunchList {
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  launches {
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    launches {
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      ...launchFragment
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    }
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  }
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}

You can define your fragment in any .graphql file. The compiler merges all .graphql files so it doesn't matter if you have multiple files or put everything in the same file.