Rendering nested form fields in Rails - ruby-on-rails

Question

In our app, we have, among others, these three models:
class PackContent < ActiveRecord::Base
belongs_to :product
belongs_to :pack
class Product < ActiveRecord::Base
has_many :pack_contents
has_many :packs, through: :pack_contents
class Pack < ActiveRecord::Base
has_many :pack_contents
has_many :products, through: :pack_contents
accepts_nested_attributes_for :pack_contents
A pack has multiple pack_contents, which are basically a product and some specific productvariants. The join table (pack_contents) looks like this:
I am now trying to display these pack_contents in a usable manner, but keep running into a wall.
I have tried:
.pack-product-rows
- #pack.pack_contents.each do |pc|
= f.simple_fields_for pc do |p|
= render :partial => 'pack_product_row', :locals => { :p => p, :pc => pc }
But then, upon saving, I get an error saying:
ActiveRecord::UnknownAttributeError in Admin::PacksController#update
unknown attribute: pack_content
And the form field name attributes are wrong, they don't account for multiple contents as they don't include an index.
When I try this:
.pack-product-rows
- #pack.pack_contents.each do |pc|
= f.simple_fields_for :pack_contents do |p|
= render :partial => 'pack_product_row', :locals => { :p => p, :pc => pc }
It renders every partial twice, which, I suppose, is to be expected.
If i don't loop over the contents and just use simple_fields_for, I get the output I want, but not how I want it. I can render the fields with p.input_field :id and the likes, but I need access to the pack_contents in order to display my data like this: (input fields meant to be hidden)
Not sure how to proceed.

Answer 1

I'm not sure if I've understood what you're asking but if you just want an access to the current item being automatically iterated via simple_fields_for, then you can access it through the form builder as p.object.

Answer 2

I am assuming that you are trying to build the nested form on the views/packs/show.html.erb where in you have the #pack instance variable initialized to a pack from the database. So on this page you will have a - simple_form_for #pack form inside which you want to nest over the pack_contents.
Now the simple_form_fields method of the simple_form gem works just like the fields_for method in rails. Based on that I am giving you the code below. It should work properly but you may have make a few syntactical changes to make it work.
- simple_form_for #pack do |pack_form|
.pack-product-rows
- #pack.pack_contents.each do |pack_content|
= f.simple_fields_for :pack_contents, pack_content do |pack_content_fields|
= render :partial => 'pack_product_row', :locals => { :pack => #pack, :pack_content => pack_content, :pack_content_fields => pack_content_fields}
Now in the partial pack_product_row you will need to use the three locals passed. You must be already using pack and pack_content but whatever fields for pack_contents you want to display should be written as pack_content_fields.field_name. If your naming convention is correct for all the fields then these fields will be either empty if the pack_content is empty or having the value stored in the database.