Using Kotlin Data Classes for CustomTypeMappings in Apollo & Android

A neat trick for working with incoming/outgoing data for GraphQL queries

For those that haven’t heard yet, GraphQL is a hot new query language for your API. The setup between ourselves and the API team had several bumps and wild cards, but we really had a great time exploring a new framework responsible for creating a GraphQL client with Android. While it took us a while to really get going, I found that working with GraphQL on Android really feels a lot more modern and a lot less clunky in comparison to the complex network layer usually required for CRUD APIs.

While this post will not discuss the intricacies of GraphQL or cover the basics of getting Android set up as a consumer client with Apollo, this short blurb covers a really neat method Ryan Casler came up taking advantage of Kotlin data classes with Apollo’s CustomTypeMapping feature.

Apollo supports custom scalar types by allowing you to define mappings in your build.gradle file. This will tell the code generator/gradle plugin what type to use when generating the class.

apollo {
   generateKotlinModels = true
customTypeMapping = [
           "AccountUserId" : "kotlin.String",
   ]
}