Overview of advanced GraphQL concepts

Out of the box, GraphQL comes with a set of scalar types:

• Int: A signed 32-bit integer
• Float: A signed double-precision floating-point value
• String: A UTF-8 encoded character sequence
• Boolean: Can be true or false
• ID: A unique identifier, serialized as a String, but meant to signify that it is not human readable

GraphQL also allows the definition of enums, which are a special kind of scalar. They are restricted to certain values. For example, we could have the following enum to distinguish different types of posts:

enum PostType {
  UNPUBLISHED,
  UNLISTED,
  PUBLIC
}

In Apollo, enums will be handled as strings that can only have certain values, but this may be different in other GraphQL implementations.

Many GraphQL implementations also allow defining custom scalar types. Apollo, for example, supports the definition of custom scalar types.

Fragments

When the same kind of...