Objects

An object is a list of fields, each of which have a name and a type. The below schema defines two object types, Post and User:

type Post {
  id: ID
  text: String
  author: User
}

type User {
  id: ID
  name: String
}

A field’s type can be any type but an input object. In the Post type, the id and text fields are scalars, while author is an object type.

When selecting a field that has an object type, at least one of that object’s fields must be selected. For instance, in the below schema, the post field is of type Post:

type Query {
  post(id: ID): Post
}

Since Post is an object type, at least one Post field must be selected in query A below—in this case, text is selected. And in query B, post.author is of type User, so at least one User field must be selected.

query A {
  post(id: "abc") {
    text
  }
}

query B {
  post(id: "abc") {
    author {
      name
    }
  }
}

In other words, we have to keep adding selection sets until we only have leaves (scalars and enums) left. Objects are the branches on the way to the leaves.