some_controller.rb

class CommentsController < ApplicationController

  def create
    translator.translate params
  end

  private
  
  def translator
    CommentRequestTranslator.new(processor)
  end

  def processor
    comment_processor = CommentProcessor.new
    comment_processor.add_listener twitter_poster
    comment_processor.add_listener facebook_poster
    comment_processor.add_listener comment_persister
    comment_processor
  end

  def twitter_poster
    TwitterPoster.new
  end

  def facebook_poster
    FacebookPoster.new
  end

  def comment_persister
    SQLCommentPersister.new
  end
end

#example class
class CommentProcessor
  def initialize
    @announcer = Announcer.new
  end

  def add_listener(listener)
    @announcer.add_listener listener
  end

  def new_comment(comment)
    new_comment = comment.with_language(language_for(comment.body))
                         .with_spam(is_spam(comment.body))
    @announcer.announce('new_comment', new_comment)
  end
end

I would agree that it can be somewhat of an issue to have the controller creating the instances of the objects. I'd generally move the creation of the objects into an infrastructure layer and then just have the controllers call into the domain. I would often however still create a "translator" or "adapter" within the controller, and pass the domain into its constructor when translation from the network request into several messages to the domain is necessary.