The GraphQL schema

The schema is the vocabulary used by GraphQL backend server, and the Relay components in the frontend. The GraphQL type system enables the schema to describe the data that's available, and how to put it all together when a query request comes in. This is what makes the whole approach so scalable, the fact that the GraphQL runtime figures out how to put data together. All we need to supply are functions that tell GraphQL where the data is. For example, in a database or in some remote service endpoint.

Let's take a look at the types used in the GraphQL schema for the TodoMVC app:

import { 
  GraphQLBoolean, 
  GraphQLID, 
  GraphQLInt, 
  GraphQLList, 
  GraphQLNonNull, 
  GraphQLObjectType, 
  GraphQLSchema, 
  GraphQLString, 
} from 'graphql'; 
 
import { 
  connectionArgs, 
  connectionDefinitions, 
  connectionFromArray, 
  cursorForObjectInConnection, 
  fromGlobalId, 
  globalIdField, 
  mutationWithClientMutationId, 
  nodeDefinitions, 
  toGlobalId...