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Variables

null in variables​

ReScript doesn't really have null, rather it has option instead. So, in its default form, all features of RescriptRelay leverages option, even if null is technically used some in GraphQL.

This mostly works out well, and gives a better experience in ReScript. However, there are cases when you need to be able to send the value null to your server in variables. For that, we have @rescriptRelayNullableVariables.

@rescriptRelayNullableVariables​

By adding this directive to your operation, you'll be able to send null (using the Js.Null module) to your server for any nullable variable (or any nullable value in any input object). It looks like this:

module Mutation = %relay(`
    mutation TestNullableVariablesMutation($avatarUrl: String) @rescriptRelayNullableVariables {
      updateUserAvatar(avatarUrl: $avatarUrl) {
        user {
          avatarUrl
        }
      }
    }
`)

// All optional variables in this operation can now be `null`, which will be preserved and sent to your server.
Mutation.commitMutation(~environment=RelayEnvironment.environment, ~variables={avatarUrl: Null})

// Or if you want to send a value:
Mutation.commitMutation(~environment=RelayEnvironment.environment, ~variables={avatarUrl: Value("some-avatar-url")})

This works for:

  • Variables in queries/mutations/subscriptions.
  • Input objects (they'll automatically be nullable when you use this directive)

The reason for this being an explicit directive and not applied globally is that this isn't the default you want, working with options is still so much easier. So, use this only when you must.