nested forms for 2 models in rails using dm-accepts_nested_attributes and dm-is-tree

I have two models: Post and Image in a forum application where Posts are arranged in parent-child format using dm-is-tree. Up this point, the images had been part of the Post model. As the Post model gets unwieldy and I need to add more depth to notating the image, I'm working to spin off the Image into its own model, but is still part of the post in output.

So I started integrating dm-accepts_nested_attributes in a simple arrangement:

class Post
  include DataMapper::Resource

  property :id, Serial                                     
  property :istop, String                                   
  property :created_at, DateTime                            
  property :updated_at, DateTime            开发者_开发知识库                
  property :content, Text                                   

  has n, :images                                           
  accepts_nested_attributes_for :images                    

  is :tree, :order => [:istop, :created_at]

class Image

  include DataMapper::Resource

  property :id, Serial
  property :created_at, DateTime

  belongs_to :post

  property :image, String, :auto_validation => false        # Carrierwave image info
  mount_uploader :image, ImageUploader                      # Carrierwave uploader

I have this form(haml) on every page for creating a post:

 = form_for [@forum,Post.new], :html => {:multipart => true} do |f|
  = f.hidden_field :istop, :value => "parent"
  = f.text_area :content
  = f.fields_for :simages_attributes do |g|
   = g.file_field :image
  .actions
   = f.submit

That goes to this controller:

def create
    @forum = Forum.get(params[:forum_id])
    @post = @forum.posts.create(params[:post])

    respond_to do |format|
      if @post.save
        format.html { redirect_to(forum_path(@forum), :notice => 'Post was successfully created.') }
      else
        format.html { redirect_to(forum_path(@forum), :notice => 'There was an error in posting') }
      end
    end
  end

The error I get when posting:

undefined method[]' for #`

, a NoMethodError

I'm not sure what I'm doing or where this is coming from at this point. I'm not sure if I have the form set-up correctly (I've been following similar active record tutorials and haven't delved into the dm-accepts_nested code at all yet). I'm able to set some even more basic stuff through the command line, but not images. I understand the basics of the nesting, but not really how to integrate it to what I'm doing atm.

Maybe someone knows. Any help appreciated.

attr_accessor :images_attributes in the Post model, allows the form to submit

However, the image is now not being saved, i.e. gets lost somewhere and isn't saved

The response I get from submitting the form:

Started POST "/forums/x/posts" for 127.0.0.1 at 2010-12-22 10:15:19 -0500
  Processing by PostsController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"/cyeRIls9M..7U8eG1lXAJg8=", "post"=>{"istop"=>"parent", "content"=>"sdfgsdfg", "images_attributes"=>{"image"=>#<File:/tmp/RackMultipart20101222-874-bhvepi>}}, "commit"=>"Create Shout", "forum_id"=>"x"}
  SQL (0.054ms)  SELECT "name" FROM "forums" WHERE "name" = 'x' ORDER BY "name" LIMIT 1
  SQL (115.419ms)  INSERT INTO "posts" ("istop", "created_at", "updated_at", "forum_name") VALUES ('parent', '2010-12-22T10:15:20-05:00', '2010-12-22T10:15:20-05:00', '', 'sdfgsdfg', 0, 'x')
Redirected to http://localhost:3000/forums/x
Completed 302 Found in 123ms

I'm guessing the form is ok, but its not saving the image.

Adding

@post.images_attributes = Image.new

or some variation to the controller does nothing so I'm curious if I need to create some sort of hook in the Post model to save the image. I do not know at this point.