Repeating form fields and updating to database - ruby-on-rails

Question

any help would be most appreciated, I am rather new to Rails.
I have two models a Shopping List and a Product. I'd like to save/update multiple products to a shopping list at a time.
The suggested changes are not updating the models. I've been googling and is "attr_accessor" or find_or_create_by the answer(s)?
Attempt 1 - Existing code
Error
> unknown attribute 'products_attributes' for Product.
Request
Parameters:
{"_method"=>"patch",
"authenticity_token"=>"3BgTQth38d5ykd3EHiuV1hkUqBZaTmedaJai3p9AR1N2bPlHraVANaxxe5lQYaVcWNoydA3Hb3ooMZxx15YnOQ==",
"list"=>
{"products_attributes"=>
{"0"=>{"title"=>"ten", "id"=>"12"},
"1"=>{"title"=>"two", "id"=>"13"},
"2"=>{"title"=>"three", "id"=>"14"},
"3"=>{"title"=>"four", "id"=>"15"},
"4"=>{"title"=>"five", "id"=>"16"},
"5"=>{"title"=>""},
"6"=>{"title"=>""},
"7"=>{"title"=>""},
"8"=>{"title"=>""},
"9"=>{"title"=>""},
"10"=>{"title"=>""}}},
"commit"=>"Save Products",
"id"=>"7"}
Attempt 2 - no errors the page reloads and none of the expected fields are updated. In earnest, I am Googling around and copying and pasting code snippets in the vain hope of unlocking the right combo.
Added to Products mode
class Product < ApplicationRecord
attr_accessor :products_attributes
belongs_to :list, optional: true
end
<%= content_tag(:h1, 'Add Products To This List') %>
<%= form_for(#list) do |f| %>
<%= f.fields_for :products do |pf| %>
<%= pf.text_field :title %><br>
<% end %>
<p>
<%= submit_tag "Save Products" %>
</p>
<% end %>
<%= link_to "Back To List", lists_path %>
list controller
def update
#render plain: params[:list].inspect
#list = List.find(params[:id])
if #list.products.update(params.require(:list).permit(:id, products_attributes: [:id, :title]))
redirect_to list_path(#list)
else
render 'show'
end
list model
class List < ApplicationRecord
has_many :products
accepts_nested_attributes_for :products
end
original do nothing - product model
class Product < ApplicationRecord
belongs_to :list, optional: true
end

Answer 1

If you just want a user to be able to select products and place them on a list you want a many to many association:
class List < ApplicationRecord
has_many :list_items
has_many :products, through: :list_products
end
class ListItem < ApplicationRecord
belongs_to :list
belongs_to :product
end
class Product < ApplicationRecord
has_many :list_items
has_many :lists, through: :list_products
end
This avoids creating vast numbers of duplicates on the products table and is known as normalization.
You can then select existing products by simply using a select:
<%= form_for(#list) do |f| %>
<%= f.label :product_ids %>
<%= f.collection_select(:product_ids, Product.all, :name, :id) %>
# ...
<% end %>
Note that this has nothing to with nested routes or nested attributes. Its just a select that uses the product_ids setter that's created by the association. This form will still submit to /lists or /lists/:id
You can whitelist an array of ids by:
def list_params
params.require(:list)
.permit(:foo, :bar, product_ids: [])
end
To add create/update/delete a bunch of nested records in one form you can use accepts_nested_attributes_for together with fields_for:
class List < ApplicationRecord
has_many :list_items
has_many :products, through: :list_products
accepts_nested_attributes_for :products
end
<%= form_for(#list) do |f| %>
<%= form.fields_for :products do |pf| %>
<%= pf.label :title %><br>
<%= pf.text_field :title %>
<% end %>
# ...
<% end %>
Of course fields_for won't show anything if you don't seed the association with records. That's where that loop that you completely misplaced comes in.
class ListsController < ApplicationController
# ...
def new
#list = List.new
5.times { #list.products.new } # seeds the form
end
def edit
#list = List.find(params[:id])
5.times { #list.products.new } # seeds the form
end
# ...
def update
#list = List.find(params[:id])
if #list.update(list_params)
redirect_to #list
else
render :new
end
end
private
def list_params
params.require(:list)
.permit(
:foo, :bar,
product_ids: [],
products_attrbutes: [ :title ]
)
end
end
Required reading:
Rails Guides: Nested forms
ActiveRecord::NestedAttributes
fields_for