Using GraphQL variables in Apollo Kotlin
GraphQL supports passing argument values to your operations with variables
. This enables you to write a single query that you can reuse with multiple variable values (this is a recommended best practice).In GraphQL, non-nullable variables are required, and nullable variables are always optional. Apollo Kotlin uses its own Optional
Consider the following GraphQL query with two nullable variables:
GraphQL
1query GetTodos($first: Int, $offset: Int) {
2 todos(first: $first, offset: $offset) {
3 id
4 text
5 }
6}Apollo Kotlin generates the following Kotlin code for this query:
Kotlin
1class GetTodosQuery(
2 val first: Optional<Int?> = Optional.Absent,
3 val offset: Optional<Int?> = Optional.Absent
4)You can then selectively provide or omit variable values like so:
Kotlin
1// Omit values for both variables
2val query = GetTodosQuery(Optional.Absent, Optional.Absent)
3// Provide null for both variables
4val query = GetTodosQuery(Optional.Present(null), Optional.Present(null))
5// Send explicit values for both variables
6val query = GetTodosQuery(Optional.Present(100), Optional.Present(0))Using input builders
For both operations and input objects, having to wrap values in an Optional
For those cases, use generateInputBuilders:
Kotlin
1apollo {
2 service("service") {
3 // ...
4 generateInputBuilders.set(true)
5 }
6}If you do, in the case of the GetTodos query shown above, Apollo Kotlin now generates a Builder for each operation:
Kotlin
1// Omit values for both variables
2val query = GetTodosQuery.Builder()
3 .build()
4// Provide null for both variables
5val query = GetTodosQuery.Builder()
6 .first(null)
7 .offset(null)
8 .build()
9// Send explicit values for both variables
10val query = GetTodosQuery.Builder()
11 .first(100)
12 .offset(0)
13 .build()