Are my ActiveRecord associations setup correctly? (simple message board application)

Basically I want a Topic to have many Posts and Posts to have many Comments. If a Post gets destroyed I want it's Comments to be destroyed. If a Topic is deleted, I want it's Posts and Comments destroyed. Does the code below accomplish this? And is the has_one :topic line necessary?

topic.rb:

class Topic < ActiveRecord::Base
  has_many :posts, :dependent => :destroy
end

post.rb:

class Post < ActiveRecord::Base
  belongs_to :topic, :depen开发者_开发百科dent => :destroy, :touch => true
  has_one    :topic
  has_many   :comments, :dependent => :destroy
end

comment.rb:

class Comment < ActiveRecord::Base
  belongs_to :post, :dependent => :destroy, :touch => true
end

Should I be using the Ancestry gem for this? Would that make this even more simple? Thanks for reading my questions. Any assistance would be greatly appreciated.

1) has_one :topic is unnecessary, with the belongs_to you already declare the association.

2) :dependent => :destroy goes on the has_many side for your requirements. If you place them on the belongs_to side you will destroy a Topic once destroying one of his posts, leaving orphan a lot of other posts.

This is the code you're looking for:

topic.rb:

class Topic < ActiveRecord::Base
  has_many :posts, :dependent => :destroy
end

post.rb:

class Post < ActiveRecord::Base
  belongs_to :topic, :touch => true
  has_many   :comments, :dependent => :destroy
end

comment.rb:

class Comment < ActiveRecord::Base
  belongs_to :post, :touch => true
end