Simple base class for service objects that implement 1) an initializer and 2) a perform method that returns a Promise

service_base.rb

# Service objects are classes that inherit from this base and implement two instance methods:
# * initialize(*args, **params) => void
# * perform() => Promise
class ServiceBase
  include ActiveModel::Validations
  
  # invokes the service and returns a Promise
  def self.perform(*args, **params)
    klass = params.any? ? new(*args, **params) : new(*args)
    klass.perform_in_transaction
  end
  
  # invokes the service. returns a value on success, and raises an exception on failure.
  def self.perform!(*args, **params)
    perform(*args, **params).unbox
  end
  
  # must be implemented by inheriting class to return a Promise
  def perform
    raise MethodNotImplemented
  end
  
  def perform_in_transaction
    instrument do
      transaction do
        perform
      end
    end
  end
  
  private def instrument
    # ... New Relic or Datadog or STATSD or what have you
  end
  
  private def transaction
    result = nil
    ActiveRecord::Base.transaction do
      result = yield
      result.rescue { raise ActiveRecord::Rollback }
    end
    result
  end
end