Auto create join table records through nested forms in rails3

So I have a model, lets call it posts.

Posts has many :tags

there is a tag join table called :tag_joins

Posts has many :tags, :through => :tag_joins

When I create a new tag, from the show view of a post, I'd like it automatically to create a record in the join table :tag_joins...

I feel like this should be possible by doing something like this in my post.rb file:

 def tag_attributes=(hash)
    hash.each do |tag_values|
      tags << Tag.build
    end
  end开发者_高级运维

But its not working..Any ideas?

Update:

The error I'm receiving currently is in the PostsController in the update block:

unknown attribute: tag

I guess accepts_nested_attributes_for :tags, :tag_joins should do the job for you