Hands-On RESTful Web Services with Go - Second Edition

Enumerations

Enumerations (Enums) are special types that give flexibility in defining a range of scalar types. They can be helpful for passing a range of information to the client. It brings the following benefits to an API:

• It allows an API to validate the field with a set of types.
• Without throwing out the type system, it communicates that the accessible field value will be in a finite set.

Let's take a look at an example schema:

type Query {  vehicle: Vehicle}enum Vehicle {  Car  Bus}type Car {  name: String,  wheels: Int}type Bus {  name: String,  wheels: Int}

In this GraphQL schema, we have a query type defined with vehicle as a field. Vehicle is an Enum. The vehicle has Car and Bus as its members. This means the query to this schema can ...