directives.md

Directives

Directives in GraphQL are extensible annotations which alter the runtime evaluation of a query or which add information to the schema definition. They always begin with an @. There are four built-in directives which this library automatically handles:

1. @include(if: Boolean!): Only resolve this field and include it in the results if the if argument evaluates to true.
2. @skip(if: Boolean!): Only resolve this field and include it in the results if the if argument evaluates to false.
3. @deprecated(reason: String): Mark the field or enum value as deprecated through introspection with the specified reason string.
4. @specifiedBy(url: String!): Mark the custom scalar type through introspection as specified by a human readable page at the specified URL.

The schema can also define custom directives which are valid on different elements of the query. The library does not handle them automatically, but it will pass them to the getField implementations through the optional graphql::service::FieldParams struct (see fieldparams.md for more information).