rom_sample.rb

require 'rom'
require 'rom-rails'

`rm -Rf /tmp/romtest.sqlite`
ROM.setup(:sql, 'sqlite:///tmp/romtest.sqlite')

class Events < ROM::Relation[:sql]
end

class Organisers < ROM::Relation[:sql]
end

class CreateEvent < ROM::Commands::Create[:sql]
  class Attributes
    include ROM::Model::Attributes

    attribute :name
    attribute :organiser_id
  end

  relation :events
  register_as :create
  result :one

  associates :organiser, key: [:organiser_id, :id]

  input Attributes
end

class CreateOrganiser < ROM::Commands::Create[:sql]
  class Attributes
    include ROM::Model::Attributes

    attribute :email
  end

  relation :organisers
  register_as :create
  result :one

  input Attributes
end

class InputMapper < ROM::Mapper
  reject_keys true

  wrap :organiser do
    attribute :email

    wrap :event do
      attribute :name, from: :event_name
    end
  end

  def call(input)
    super([input]).first
  end
end

class Validator
  include ROM::Model::Validator

  validates :event_name, presence: true
end

ROM.finalize
rom = ROM.env
gateway = rom.gateways.fetch(:default)

migration = gateway.migration do
  change do
    create_table :organisers do
      primary_key :id
      column :email, String, null: false
    end

    create_table :events do
      primary_key :id
      column :name, String, null: false
      column :organiser_id, Integer, null: false
    end
  end
end

migration.apply(gateway.connection, :up)

command = rom.command([
  { organiser: :organisers }, [:create, [
    { event: :events }, [:create]
  ]]
])

input = {
  email:      'test@example.com',
  event_name: 'Test Event'
}

mapper = InputMapper.build
validator = Validator.new(input)

if validator.valid?
  result = command.call(mapper.call(input))

  puts result
  # {:id=>1, :email=>"test@example.com"}
  # {:id=>1, :name=>"Test Event", :organiser_id=>1}
end