Operator Composition

This example illustrates the concept of composition in GraphQL, which allows you to combine multiple operations (known as "operators") to build more complex transformations of data.

The given schema is defining two data types - User and Post. The User type has fields id and name, and the Post type initially has fields user and userId.

type User {
  id: Int
  name: String
}

type Post @addField(name: "userName", path: ["user", "name"]) {
  user: User @modify(omit: true) @http(path: "/users/{{userId}}")
  userId: Int!
}

However, it uses a series of operators to modify the user field.

1. The @addField(name: "userName", path: ["user", "name"]) operator is used to extract the name field from user and add a field called userName to the Post

2. The @modify(omit: true) operator is used to remove the user field from the final Schema.

3. The @http(path: "/users/{{userId}}") operator is used to instruct the resolver to make an HTTP request to fetch the user data from a specified path (i.e., /users/{{userId}}), where {{userId}} is a placeholder that would be replaced with the actual userId when making the request.

The schema after this transformation looks like this:

type User {
  id: Int
  name: String
}

type Post {
  userName: String
  userId: Int!
}

So, we've used composition of operators to take a complex object (the User inside the Post), extract a specific part of it (name), name that part (userName), and then instruct GraphQL how to fetch the data using an HTTP request.

info

It is important to note that the order of the operators @modify and @http doesn't matter. The resulting schema will always be the same.

This is a powerful mechanism that allows you to make your GraphQL schema more precise, easier to understand, and more suitable for the specific needs of your application.