Post.js

class Post {
  static Resource = HttpResource;
  static resourceConfig = { endpoint: '/posts' };

  @field({ required: true }))
  title = 'untitled';

  @field()
  text = '';

  @field({ type: GraphQLInt })
  number;

  @relationship(() => Author, { authorId: GraphQLString }, { required: True })
  author;

  // Or maybe:
  @field({ required: True }))
  author = relationship(() => Author, { authorId: GraphQLString });

  @method({ input: GraphQLInt }, GraphQLInt)
  square({ input }) {
    return input * input;
  }

  // Not included on the GraphQL type.
  propValue = 4;

  static extraFields = () => ({
    extraField: {
      type: GraphQLInt,
      resolve: () => 3,
    },
  });

  static mutations = [
    CreateMutation,
    UpdatePartialMutation,
    DeleteMutation,
  ];
}

// So then when needed you could do:
Author.getResource(context)
Author.Type
Author.ConnectionType

// For a Relay server, you could do:
class Author extends NodeModel { /* ... */ }

Post.orm.js

// Imagine orm.Post is a Mongoose model or something equivalent.

class Post extends OrmModel(orm.Post) {
  static fields = {
    number: GraphQLInt,
    propValue: null, // Or have a separate excludeFields?
    // The rest get included by default.
  }

  // Maybe?
  static methods = {
    square: [{ input: GraphQLInt }, GraphQLInt],
  }

  static extraFields = () => ({
    extraField: {
      type: GraphQLInt,
      resolve: () => 3,
    },
  });

  static mutations = [
    CreateMutation,
    UpdatePartialMutation,
    DeleteMutation,
  ];
}