Factory method using convention and ruby

controllers.rb

class ApplicationController < ActionController::Base

  # other stuff ..

  def notify(*args)
    Notifications::Notifier.new.notify(*args) 
  end
end

class CommentsController < ApplicationController
  # other stuff

  def create
    @comment = task.new_comment(params[:comment])
  
    if @comment.save
      notify :new_comment, @comment
      # render comment
    else
      # render errors
    end
  end 
end

example.rb

Notifications::NewComment.create(comment)
Notifications::NewIdea.create(idea)

notifier.rb

module Notifications
  class Notifier
    def notify kind, *args
      notification_class(kind).create(*args)
    end

    private

    def notification_class(kind)
      "Notifications::#{kind.to_s.camelize}".constantize
    end
  end
end