How do I manually set nested model values in Rails 3 before saving?

I have a single text area input that I would like to get as a blob my new method on my controller, but would like to parse and otherwise mess with the input before it's saved.

I know I can arbitrarily set attributes on a model by saying something like

@post.user_id = current_user.id

where that attribute isn't coming directly from a form. My issue here though is that I want to set a nested model's values.

Let's say the association is post has_many comments 开发者_StackOverflowand comment belongs_to post

Does post.comments just get set to a hash that looks like comments? Like

@post.comment = {'comment' => 'foo'}

Or something similar?

Thanks for any guidance on this.

---

Usually I'd say it's best to DRY up this sort of thing and just handle the parsing on the comments model itself with a before_save callback.

class Comment < ActiveRecord::Base
  before_save :parse_comment

  protected
  def parse_comment
    self.comment = ...
  end
end

But if a callback isn't going to work for you, @corroded's suggestion should work.

---

if you have nested form fors, you can just get the comment values from your params via:

@post.comment.update_attributes(params[:comment])

(you should have called @post.build_comment in your #new though)

If you're looking to set them in your controller, then you need a hash 'container' for your comment like so:

{'comment' => {:message => 'foo', :author => current_user}}

or something like that