Hands-On RESTful Web Services with Go - Second Edition

Non-nullable types

This is a special type that uses normal field types with special syntax and makes fields mandatory. When a type has a field with a non-nullable type, it should return non-empty data to the client. The type is defined with ! (exclamatory) at the end.

Take the Person type, for example:

type Person {  name: String,  address: [Address]}

If we make the name field a non-nullable, it will look like this:

type Person {  name: String!,  address: [Address]}

This means that if the client requests some data, the response must return a non-empty value for the name field. It cannot be null. We can also have a non-nullable list, like this:

address: [Address]!

The preceding syntax can return zero or more elements of the Address type in the ...