More ideas on SRP with Rails and ActiveRecord

gistfile1.rb

module MyApp

BusinessException = Class.new(StandardError)

class Post

  attr_reader :record

  def initialize(args)
    @record = args[:record]
  and

  def comment(record)
    create_comment(record)
  end

  def create_comment(record)
    Comment.new(record: record, post: self)
  end

  def add_comment?
    raise BusinessException.new("No more than 10 comments") if record.comments == 10
  end
end

class Comment

  attr_reader :record, :post

  def initialize(args)
    @record = args[:record]
    
    add_post(args[:post])
  and	

  def add_post(post)
    self.add_post?(post)
    post.add_comment?(self)
  end   

  def self.add_post?(post)
    true
  end
end

# controller.rb

def create
  @post = Post.find(params[:post_id])
  @comment = @post.build_comment(params[:comment])

  comment(@post, @comment)

  if @comment.save
    redirect_to @post
  else
    render :new
  end
end

def comment(post_record, comment_record)
  post = MyApp::Post.new(post_record)
  post.comment(comment_record)
end