LightServiceObject

Add this line to your application's Gemfile:

gem 'ensurance'  # Optional
gem 'light_service_object'

And then execute:

$ bundle

Service objects are a great way to encapsulate business/domain functionality in a Rails app.

They typically wrap some functionality up in a call method, with an initializer for setting parameters.

class TypicalServiceObject
  def initialize(date, number)
    @date = date
    @number = number
  end

  def call
    @date = Date.parse(@date) if @date.is_a?(String)
    If @date - Date.today < 7 then
      @number += 10
    else
      raise ArgumentError.new("Date is too far away")
    end
    @number
  end
end

This service object has a few problems:

• No indication of what it's "contract" is with the outside world
• No way to indicate failure other than Exceptions
• Manual conversion of data into the expected form

class NewServiceObject < LightServiceObject::Base
  required :date, ensure: Date
  optional :number

  def perform
    fail!("Date is too far away") if date - Date.today >= 7

    number + 10
  end
end

• date is required, a failure will be returned with the error message
• date will be transformed into a Date if it isn't one already ensure: Date
• fail!(message) causes the service to return a failure and message
• the last thing evaluated will be returned as the result number + 10
• one side note: all parameters are immutable by default

It really is just a plain-old-ruby-object (PORO) with Dry::Initializer throw in with some syntax grease, and returns a Dry::Monads::Result -- that's it.

Bug reports and pull requests are welcome on GitHub at https://github.com/bsharpe/light_service_object.

The gem is available as open source under the terms of the MIT License.