user.rb

## somewhere.rb

bunch_of_user_entities = UserRepository.new.fetch_all_active_users.map do |user_record|
  UserEntity.new(user_record.id, user_record.email, user_record.name, user_record.age)
end

## user_entity.rb

class UserEntity < Struct.new(:id, :email, :name, :age)
  def to_s
    "#{name}-#{email}"
  end
end

## user_repo.rb

class UserRepository
  def fetch_all_active_users
    Query.active_users
  end

  def fetch_all_active_male_users
    Query.active_users.gender(:male)
  end

  def fetch_users_older_than_21
    Query.older_than(21)
  end
end

## user_query.rb

class UserQuery
  def self.active_users
    where(status: :active)
  end

  def self.gender(g)
    where(gender: g)
  end

  def self.older_than(age)
    where(dob > age.years.ago)
  end
end