Rails 4 where not sending id - ruby-on-rails

Question

Ruby on Rails 4
My Form was working great when I had Product.all:
<div id="ip_voice">
<%= f.label :product_id %><br>
<%= f.collection_select :product_id, Product.all, :id, :name, {prompt: "Select a product"}, {class: "form-control input-lg"} %>
</div>
I changed it to a Product.where so I could show different options based on another selection, but this is not sending the :id of the Product. I am new to Rails 4.
<div id="ip_voice">
<%= f.label :product_id %><br>
<%= f.collection_select :product_id, Product.where({ category: "ip_voice" }), :id, :name, {prompt: "Select a product"}, {class: "form-control input-lg"} %>
</div>
My log, shows the product_id field as "" which is not allowed.
Started POST "/mc_question" for x at 2014-04-25 10:05:13 -0700
Processing by QuestionsController#create as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"x=", "question"=>{"content"=>"what is going on", "category"=>"ip_video_telephon
y", "product_id"=>"", "active"=>"1", "question_type"=>"MC", "answers_attributes"=>{"0"=>{"content"=>"what", "correct"=>"0"}, "1"=>{"content"=>"is", "correct"=>"1"}, "2"=>{"
content"=>"up", "correct"=>"0"}, "3"=>{"content"=>"", "correct"=>"0"}}}, "commit"=>"Create Question"}
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."remember_token" = 'x' LIMIT 1
(0.1ms) begin transaction
(0.0ms) rollback transaction
The div ip_voice is one of six. Onle one is show() the others are hide(). Don't think that matters though. Like this:
<div id="ip_video_surveillance">
<%= f.label :product_id %><br>
<%= f.collection_select :product_id, Product.where({ category: "ip_video_surveillance" }), :id, :name, {prompt: "Select a product"}, {class: "form-control input-lg"} %>
</div>
<div id="ip_video_telephony">
<%= f.label :product_id %><br>
<%= f.collection_select :product_id, Product.where({ category: "ip_video_telephony" }), :id, :name, {prompt: "Select a product"}, {class: "form-control input-lg"} %>
</div>
HTML Names are the same:
<div id="ip_voice">
<label for="question_product_id">Product</label><br>
<select class="form-control input-lg" id="question_product_id" name="question[product_id]"><option value="">Select a product</option>
<option value="2">thisone</option>...
</div>
<div id="ip_video_surveillance">
<label for="question_product_id">Product</label><br>
<select class="form-control input-lg" id="question_product_id" name="question[product_id]"><option value="">Select a product</option>...
Any help appreciated.

Answer 1

If you have six f.collection_select :product_id then most likely they all have same name attribute for <select>. Try to check it in generated HTML.
In that case you have to use different names.
upd: Your question[product_id] passed as "question"=>{"product_id"=>""}
params quacks like a Hash. So all following values will override previuos:
> params = ActionController::Parameters.new(question: { product_id: 1 })
=> {"question"=>{"product_id"=>1}}
> params[:question][:product_id] = ""
=> ""
> params
=> {"question"=>{"product_id"=>""}}

Answer 2

Try giving it as a scope in your model and use that in collection_select
#=>product.rb
class Product < ActiveRecord::Base
scope :category, -> { where(category: "ip_voice") }
end
<div id="ip_voice">
<%= f.label :product_id %><br>
<%= f.collection_select :product_id, Product.category, :id, :name, {prompt: "Select a product"}, {class: "form-control input-lg"} %>
</div>
Edit
In your products_controller.rb assign the scope to an instance variable like this
def your_method
#product_categories = Product.category
end
and use in the form in place of Product.category
<div id="ip_voice">
<%= f.label :product_id %><br>
<%= f.collection_select :product_id, #product_categories, :id, :name, {prompt: "Select a product"}, {class: "form-control input-lg"} %>
</div>