nested image model objects not showing on edit action - ruby-on-rails

Question

I've been ignoring this problem for a while but I can't any longer. My nested image model objects, product_images are not showing when I render a product's edit view. Due to this my application calls an error saying that the image is nil when I try to render the show view.
Why arent my nested product images appearing? I'm using paperclip and s3.
I need the nested images form to be editable, everything works when a new product is created, the editing is the only problem. The nil exception during the show action is just related to the edit action malfunction
Below is my code:
models ##
class ProductImage < ActiveRecord::Base
attr_accessible :product_id, :photo, :image_width, :image_height
belongs_to :product
has_attached_file :photo, :styles => { :small => "150x150>"}, :dependent => :destroy
validates_attachment_presence :photo
validates_attachment_size :photo, :less_than => 5.megabytes
validates_attachment_content_type :photo, :content_type => ['image/jpg', 'image/jpeg', 'image/png', 'image/gif']
after_post_process :save_image_dimensions
def save_image_dimensions
geo = Paperclip::Geometry.from_file(photo.queued_for_write[:original])
self.image_width = geo.width.to_i
self.image_height = geo.height.to_i
end
def sized_different?
if image_width < image_height
true
else
false
end
end
end
class Product < ActiveRecord::Base
attr_accessible :taxable, :shippable, :page_name, :tact_code, :manu_code, :body_code, :name, :alert, :price, :description, :colors_attributes, :sizes_attributes, :extras_attributes, :restraints_attributes, :product_images_attributes
validates_presence_of :page_name
validates_presence_of :price
validates_presence_of :description
validates_presence_of :name
has_many :product_images, :dependent => :destroy
has_many :restraints, :dependent => :destroy
has_many :colors, :dependent => :destroy
has_many :sizes, :dependent => :destroy
has_many :extras, :dependent => :destroy
accepts_nested_attributes_for :colors, :sizes, :extras, :restraints, :product_images
end
controller
def index
#products = Product.search(params)
unless current_cart.nil?
#cart = current_cart
else
#cart = nil
end
end
def new
#product = Product.new
#product.product_images.build
end
def create
#product = Product.new(params[:product])
if #product.save
render :index
else
render :new
end
end
def edit
#product = Product.find(params[:id])
#cart = current_cart
end
def show
#product = Product.find(params[:id])
#cart = current_cart
end
def update
#product = Product.find(params[:id])
if #product.update_attributes!(params[:product])
render :index
else
render :edit
end
end
end
_form view
<%= form_for #adminproduct, validate: true, html:{ multipart: true} do |f| %>
<div class="span3 field">
<ul class="unstyled">
<li><%= f.text_field :name, :placeholder => "Product name" %></li>
<li><%= f.text_field :manu_code, :placeholder => "Manufacturer code" %></li>
<li><%= f.text_field :alert, :placeholder => "Alert, example: Save 10%" %></li>
<li><%= f.text_field :price, :placeholder => "Base price" %></li>
<li><%= f.text_area :description, :placeholder => "Product description", :size => "30x10" %></li>
</ul>
</div>
<div class="span6 offset1">
<ul class="unstyled">
<li><%= f.check_box :taxable %>Item can be taxed</li>
<li><%= f.check_box :shippable%>Item can be standard shipped</li>
<li><br /><b>Choose product images:</b></li>
(the first image will be the product's main image)<br/>
<%= f.fields_for :product_images do |p|%><%= render 'product_image_fields', f: p %><% end %>
<li><%= link_to_add_fields "Add image", f, :product_images %></li>
Any insight is appreciated.
edit
product images partial
<fieldset>
<%= f.file_field :photo %>
<%= f.hidden_field :_destroy %>
<%= link_to "remove", '#', class: "remove_fields" %>
</fieldset>

Answer 1

On the products_controller, modify the edit action to include product_images so that accepts_nested_attributes_for knows which images to update.
def edit
#product = Product.includes(:product_images).find(params[:id])
# ...
end

Answer 2

I believe you need to call your partial like this:
<%= render partial: 'product_image_fields', locals: {f: p} %>
If it does not work, please paste in your original question your 'product_image_fields' file and the error message from your console
--
Ok this is your partial
<fieldset>
<%= f.file_field :photo %>
<%= f.hidden_field :_destroy %>
<%= link_to "remove", '#', class: "remove_fields" %>
</fieldset>
A your problem is empty product_image upload inputs. Well you using file_field, which produce input type=file, and HTML won't allow you to put a value in this kind of fields. In other words: you cannot load value from a database to a file_field.
This is my advise:
Change your partial to output what comes from the database. This is just to verify and confirm the data arrive at the right place
<fieldset>
<%= f.object.send :photo %>
<%= f.file_field :photo %>
<%= f.hidden_field :_destroy %>
<%= link_to "remove", '#', class: "remove_fields" %>
</fieldset>
You should get in the screen the path of your image. Also look at the HTML source, Rails should add hidden fields with your images records id.
If you got all right, then you need to display your image with something else than a file_field, try an image_tag or anything else you want to use

Answer 3

Have you tried you tried using the wonderful accepts_nested_attributes_for provided by Rails for working with Nested Attributes?
Read more http://api.rubyonrails.org/classes/ActiveRecord/NestedAttributes/ClassMethods.html
EDIT
I thought best to provide you an example rather.
class Product < ActiveRecord::Base
attr_accessible ..., :product_images_attributes # <======= Pay attention here. Mass Assignment attributes required
accepts_nested_attributes_for :product_images
....
end