service-objects

class UserRegistrationService
  class Result
    attr_reader :user, :errors

    def initialize(success:, user: nil, errors: [])
      @success = success

class CheckoutService
  def initialize(cart:, user:)
    @cart = cart
    @user = user
  end

class RevenueStat
  DEFAULT_RANGE = 30.days

  def initialize(account, range: DEFAULT_RANGE)
    @account = account
    @range = range

class ApplicationCommand
  Result = Struct.new(:value, :errors) do
    def success?
      errors.nil? || errors.empty?
    end

module Result
  def self.Success(value)
    Success.new(value)
  end

  def self.Failure(error)

module BoundedFanOut
  Result = Struct.new(:value, :error) do
    def ok?
      error.nil?
    end
  end

module Posts
  class CreateService
    def initialize(author:, params:)
      @author = author
      @params = params
    end

module EventBus
  @subscribers = Hash.new { |h, k| h[k] = [] }

  class << self
    def subscribe(event_class, handler = nil, &block)
      callable = handler || block