Base service object

domain_service.rb

require "concord"
require "procto"

# Small wrapper module for domain services.
#
# Creates a service object with a ::call method that delegates to the instance
# method name given in the `call` option. Defaults to :call. (Procto)
#
# Provides initializer arguments, sets the ivars, and optional public reader
# methods for the attribute names passed in for `attrs`. (Concord)
#
# Example:
#
# class CreateSomethingService
#   include DomainService.new(:thing1, :thing2)
#
#   def call
#     # do stuff to thing1 and thing2
#   end
# end
#
# CreateSomethingService.call(my_thing1, my_thing2)
#
# # or
#
# service = CreateSomethingService.new(my_thing1, my_thing2)
# service.my_thing1
# #=> my_thing1
# service.my_thing2
# #=> my_thing2
# service.call # same as the first ::call
#
# Inherits from Module to give us the include syntax
class DomainService < Module
  # include DomainService.new(...)
  # attrs - Attribute names for Concord
  # call - Instance method to call from ::call
  def initialize(*attrs, call: :call)
    @attrs = attrs
    @call = call
  end

  # Called when module is included.
  def included(descendant)
    # Provides ::call method that delegates to #call
    descendant.send(:include, Procto.call(@call)) # rubocop:disable LambdaCall
    # Provides #new and sets ivar + optional public reader
    descendant.send(:include, Concord::Public.new(*@attrs))
    # Define Failure error on module/class
    descendant.const_set "Failure", failure_error_class
  end

  # General Failure from service, defined as a subclass of StandardError.
  # An object can be passed in so the rescue block can inspect and use
  # error data. For instance with AR Model errors.
  def failure_error_class
    Class.new(StandardError) do
      include Concord::Public.new(:object)
    end
  end
end