many_commands.rb

require 'rom'
require 'virtus'

ROM.setup :memory

class User
  include Virtus.model

  attribute :name, String
  attribute :role, Symbol, default: 'user'
end

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

class UserMapper < ROM::Mapper
  relation :users
  register_as :entity

  model User
end

class CreateAdmin < ROM::Commands::Create[:memory]
  relation :users
  register_as :create_admin
  input ->(user) { user.merge(role: 'admin') }
end

class CreateManager < ROM::Commands::Create[:memory]
  relation :users
  register_as :create_manager
  input ->(user) { user.merge(role: 'manager') }
end

class CreateUser < ROM::Commands::Create[:memory]
  relation :users
  register_as :create_user
end

ROM.finalize

rom = ROM.env

create_admin = rom.command(:users).create_admin
create_manager = rom.command(:users).create_manager
create_user = rom.command(:users).create_user

create_admin.call(name: 'John Doe')
create_manager.call(name: 'John Snow')
create_user.call(name: 'Nobody')

p rom.relation(:users).to_a
# => [{:name=>"John Doe", :role=>"admin"}, {:name=>"John Snow", :role=>"manager"}, {:name=>"Nobody"}]

p rom.relation(:users).as(:entity).to_a
# => [#<User:0x007fe249896f60 @name="John Doe", @role=:admin>, #<User:0x007fe249894670 @name="John Snow", @role=:manager>, #<User:0x007fe2498943f0 @name="Nobody", @role=:user>]