Nested comments on a Blog using MongoMapper

nested.rb

# Be sure to have mongod running
# Below is an attempt to show one way to have nested comments on a blog post
# I did not thoroughly examine whether it is bulletproof or performant. 
# But it seems to work :-)

col = Blog.all()
col.each {|c| c.destroy }
col = Comment.all()
col.each {|c| c.destroy }

class Blog
  include MongoMapper::Document
  key :title, String
  many :comments
  
  def to_s
    puts "\n----------\n#{title}"
    comments.each do |c|
      c.to_s if c.comment_id.nil?
    end
  end
end

class Comment
  include MongoMapper::Document
  key :text, String
  
  many :comments
  key :comment_id, ObjectId
  belongs_to :comment
  
  key :blog_id, ObjectId
  belongs_to :blog
  
  def to_s(depth = 1)
    prefix = "\t"*depth
    puts "#{prefix}#{text}"
    comments.each do |c|
      c.to_s(depth+1)
    end
  end
end

blog = Blog.create(:title => "Greatest Idea Ever" )
c1 = Comment.create( :text => "Comment 1", :blog => blog)
c2 = Comment.create(:text => "Comment 2", :blog => blog)

c11 = Comment.create(:text => "Comment 1 - 1", :blog => blog, :comment => c1)
c12 = Comment.create(:text => "Comment 1 - 2", :blog => blog, :comment => c11)
blog.to_s


# OUTPUT:
# ----------
# Greatest Idea Ever
# 	Comment 1
# 		Comment 1 - 1
# 			Comment 1 - 2
# 	Comment 2