Functional Ruby

examples.rb

# - Reusable, immutable objects
# - Inject dependencies in constructor

class UserQuery
  attr_reader :query

  def initialize(query)
    @query = query
  end

  def with(query)
    self.class.new(query)
  end

  def call
    query.execute
  end
end

# `PersistPerson` is bound the the interface of user_repository, which is better
# than being bound to, say, the hardcoded class name.
class PersistPerson
  attr_reader :user_repository

  def initialize(user_repository)
    @user_repository = user_repository
  end

  def call(person)
    user_repostiory.save(person)
  end
end