Unpermitted parameters for Dynamic Forms in Rails 4 - ruby-on-rails

Question

I'm new to Rails and built something based on this
http://railscasts.com/episodes/403-dynamic-forms
but I have a problem with storing data in the additional fields...
I have a ProductType object that has many ProductField objects. The ProductField object also belongs to a ProductType and Product object belongs to a ProductType.
So,new dynamic fields can easily be added via the constructor ProductType, but when I try to set data in this fields via Product controller nothing happens.
I am sure that problem is related to use strong parameters, but fix described here and here did't help.
product.rb
class Product < ActiveRecord::Base
belongs_to :product_type
serialize :properties, Hash
end
product_type.rb
class ProductType < ActiveRecord::Base
has_many :fields, class_name: "ProductField"
accepts_nested_attributes_for :fields, allow_destroy: true
end
product_field.rb
class ProductField < ActiveRecord::Base
belongs_to :product_type
end
products_controller.rb
class ProductsController < ApplicationController
def new
#product = Product.new(product_type_id: params[:product_type_id])
end
def product_params
params.require(:product).permit(:name, :price, :product_type_id, {:properties => []})
end
product_type_controller.rb
class ProductTypesController < ApplicationController
def product_type_params
params.require(:product_type).permit(:name, fields_attributes: [:id, :name, :field_type, :required, :product_type_id])
end
In console log:
Unpermitted parameters: properties
Started PATCH "/products/4" for 127.0.0.1 at 2013-10-04 22:54:59 +0400
Processing by ProductsController#update as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"my3ra60OUXexmmguk2eqRetizx3tWPMq04Z2PnODJMQ=", "product"=>{"product_type_id"=>"1", "name"=>"Product1", "properties"=>{"gjfghjf"=>"123", "123"=>[""]}, "price"=>"10"}, "commit"=>"Update Product", "id"=>"4"}
Product Load (0.3ms) SELECT "products".* FROM "products" WHERE "products"."id" = ? LIMIT 1 [["id", "4"]]
Unpermitted parameters: properties
P.S: maybe someone faced a similar problem when watching a podcast?

Answer 1

If you want to return a nested hash as a parameter you have to name the keys in the array in permit.
class ProductsController < ApplicationController
def new
#product = Product.new(product_type_id: params[:product_type_id])
end
def product_params
params.require(:product).permit(:name, :price, :product_type_id, {:properties => [:foo, :bar, :id]})
end
If you are generating the keys dynamically and can't code them into the permit statement then you need to use this style:
def product_params
params.require(:product).permit(:name, :price, :product_type_id).tap do |whitelisted|
whitelisted[:properties] = params[:product][:properties]
end
end
It's not the most friendly code for a new user, I just finished the 3 course rails certificate at UW and they never even covered .tap.
This is not my work, I'm still just understanding the deeper parts of .permit like this. This is the blog entry I used: Strong Parameters by Example