Mapping raw tuple to jsonapi using rom-mapper and yaks

json_api.rb

require 'anima'
require 'rom-mapper'
require 'yaks'

class User
  include Anima.new(:id, :first_name, :last_name, :posts)
end

class Post
  include Anima.new(:id, :title)
end

class UserMapper < ROM::Mapper
  reject_keys true

  model User

  attribute :id
  attribute :first_name, from: :name
  attribute :last_name

  group :posts do
    model Post

    prefix :post

    attribute :id
    attribute :title
  end
end

module JsonAPI
  class UserMapper < Yaks::Mapper
    attributes :id, :first_name, :last_name

    has_many :posts
  end

  class PostMapper < Yaks::Mapper
    attributes :id, :title
  end
end

struct = [{
  id: 1,
  name: 'Jane',
  last_name: 'Doe',
  post_id: 1,
  user_id: 1,
  post_title: 'Foo'
}, {
  id: 1,
  name: 'Jane',
  last_name: 'Doe',
  post_id: 2,
  user_id: 1,
  post_title: 'Bar'
}]

yaks = Yaks.new do
  # default_format :hal
  default_format :json_api
  mapper_namespace JsonAPI
end

print yaks.call(UserMapper.build.call(struct))