gistfile1.rb

# Creates 'x' categorizations with null category_id's
  def create
    @user = current_user
    @post = @user.posts.create(params[:post])
    @categories = @user.categories.all
    @post.categorizations.build(:category_id => params[:categorization_ids])
    params[:categorization_ids].each do |categorization|
      @post.categorizations.build(params[:categorization_id])
    end
  end
 
# Form and nested form below
= form_for [@user, @post] do |f|
  .field
    .radio_brick.add_new.upload_image
      %a.big_link
        %i Q
      %h4 Upload Image
      %h5
        Drag an image here or
        %a{:href => "#", :id => "browse_file"}
          browse
        for an image to upload.
      %h4.file_name
    = f.file_field :thumbnail_image, :class => 'hidden', :id => "post_upload"
  .field
    %span Title:
    = f.text_field :name
  .field
    %span Subtitle:
    = f.text_field :subtitle
  .field
    %span Tags:
    = f.text_field :tag_list
  .field.no_border.summary
    %span Summary:
    = f.text_area :summary
 
  %ul
    = f.fields_for :categorization do |categorization|
      - @categories.each do |category|
        %li
          = check_box_tag 'categorization_ids[]', category.id
          = category.title