Input & Output Types

GraphQL makes a clear distinction between input and output types. Input types are concerned with the arguments to our resolvers, and output types are concerned with what we return from our resolvers. Certain types such as scalars can appear both as an input or an output type. However, many input and output types are mutually exclusive.

Neutral Types

All scalars, enums, and lists of neutral types fall under this category. For example:

  • String
  • Float!
  • enum Membership { free, paid, enterprise }
  • [String]
  • [Membership!]

Output Types

All neutral types, objects, unions, interfaces, and lists of output types fall under this category. The fields of an object type may only be other output types. For example:

  • String
  • enum Membership { free, paid, enterprise }
  • type User { id: ID!, membership: Membership! }
  • [User]

Input Types

All neutral types, input objects and lists of input types fall under this category. The fields of an input object type may only be other input types

  • String
  • enum Membership { free, paid, enterprise }
  • input SignupArgs { fullName: String!, membership: Membership! }

In uniform-graphql, the type system will guide you and make sure that you don’t accidentally mix input types and output types.

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