Manual ROM env setup

manual_rom_env_setup.rb

require "rom/memory"

memory_repo = ROM::Memory::Repository.new
user_dataset = memory_repo.dataset(:users)

class Users < ROM::Relation[:memory]
end

class UserMapper < ROM::Mapper
  model name: 'UserEntity' # ROM supports generating model classes
  attribute :name
end

user_relation = Users.new(user_dataset)
user_mapper = UserMapper.build # using build injects default mapper processor

user_relation.insert(name: 'Jane')

puts user_mapper.call(user_relation).to_a.inspect