Couldn't find Manufacturer with 'id'= (blank) - ruby-on-rails

Question

I am trying to create a web application to practise my Ruby on Rails skill. I have a few entities in my database manufacturers, models, tints, prices
manufacturers {id, name} - stores the make of the car
models {id, manufacturer_id, name} - stores the models of the car
tints {id, manufacturer_id, model_id, front, sides, rear} - stores the length of tint required
prices {id, description, price } - stores the price of the item
I created a page to generate a quotation for window tinting. The page includes drop-down menus to let user to select manufacturer, model, type of film(front), type of film(side+rear)
Below is the code for the form
<%= form_tag('/quotation/tints/generate') do %>
<%= label :manufacturer_id, 'Manufacturer' %>
<div class="field">
<%= collection_select(:tint, :manufacturer_id, Manufacturer.order(:name), :id, :name, {:prompt => "Select Manufacturer"}) %>
</div>
Model:
<div class="field">
<%= grouped_collection_select(:tint, :model_id, Manufacturer.order(:name), :models, :name, :id, :name, {:prompt => "Select Model"}) %>
</div>
<%= label :price_front, 'Front Tint' %>
<div class="field">
<%= collection_select(:price, :price_front, Price.order(:name), :id, :name, {:prompt => "Select Front Tint"}) %>
</div>
<%= label :price_rear, 'Size and Back Tint' %>
<div class="field">
<%= collection_select(:price, :price_rear, Price.order(:name), :id, :name, {:prompt => "Select Side & Rear Tint"}) %>
</div>
<div class="form-group">
<%= submit_tag 'Submit' %>
</div>
<% end %>
When the form is submitted, it should be redirected to /quotation/tints/generate and display the value from the dropdown menu. However, I received an error, saying that Couldn't find Manufacturer with 'id'=. The code that caused the error is shown below
def generate
#manufacturers = Manufacturer.find(params[:manufacturer_id])
end
Here is the parameter from the debug log
{"utf8"=>"✓",
"authenticity_token"=>"Pl2bXiRT0AoF4i0h1RCHDbuvaKJNZOkV5ULQHKxDQgZzBWWLJ2mH7ddb9akwgxbloxBIHoVaT3pcwoIGcRufpg==",
"tint"=>{"manufacturer_id"=>"7", "model_id"=>"6"},
"price"=>{"price_front"=>"1", "price_rear"=>"2"},
"commit"=>"Submit"}
I can see that the id of each drop down value are shown up correctly in the parameter list. However, I coundn't able to print the value at /quotation/tints/generate nor get the name of the manufacturer or model.
Here is routes.rb:
get '/quotation/tints' => 'tints#quotation', :as => 'tints_quotation'
post '/quotation/tints/generate' => 'tints#generate', :as => 'generate_tints_quotation'
Tint.rb:
class Tint < ApplicationRecord
has_many :manufacturers
has_many :models
belongs_to :manufacturer
belongs_to :model
validates_uniqueness_of :model_id, :scope => [:manufacturer_id]
end
Model.rb:
class Model < ApplicationRecord
belongs_to :manufacturer, :dependent => :destroy
validates :name, :presence => true
validates_uniqueness_of :name, :scope => [:manufacturer_id]
before_save :capitalize_content
end
Manufacruter.rb:
class Manufacturer < ApplicationRecord
has_many :models, :dependent => :destroy
validates :name, :presence => true, uniqueness: { case_sensitive: false }
before_save :capitalize_content
end
tints.controller.rb:
def quotation
render 'quotation'
end
def generate
#manufacturers = Manufacturer.find(params[:manufacturer_id])
end
generate.html.erb:
<%= #manufacturers.name %>
I'm trying to print the manufacturer selected
I have tried multiple ways to define it, but I am still facing the same error. Any help is greatly appreciated.

Answer 1

In your params, manufacturer_id is a nested value of tint, as opposed to being a direct key of the params hash. Try the following:
def generate
#manufacturers = Manufacturer.find(params[:tint][:manufacturer_id])
end