mom_minimal.rb

require 'mom'

entities = Mom::Registry.build do # build models using :anima
  register :user do
    map :id
    map :name
    group :tasks
  end

  register :task do
    map :id
    map :title
  end
end

entity = entities[:user]
hash   = {id: 1, name: 'snusnu', tasks: [{id: 1, title: 'doit'}]}

user_obj  = entity.load(hash)
user_hash = entity.dump(user_obj)

puts "loaded: #{user_obj.inspect}"
puts "dumped: #{user_hash.inspect}"

__END__

loaded: #<Entity(user) id=1 name="snusnu" tasks=[#<Entity(task) id=1 title="doit">]>
dumped: {:id=>1, :name=>"snusnu", :tasks=>[{:id=>1, :title=>"doit"}]}