Building Rails Forms for saving Polymorphic Associations - ruby-on-rails

Question

I have categories model which I would like to be able to use with different models. That's how I ended up using Polymorphic with has_many.
With Rails_admin everything works without a problem. But, when I want to create a form by myself, I can't seem to make it save. Here is what I have:
category.rb
class Category < ActiveRecord::Base
has_many :categorizings, inverse_of: :category, dependent: :destroy
has_many :cars, through: :categorizings, :source => :categorizable,
:source_type => 'Car'
end
categorizing.rb
class Categorizing < ActiveRecord::Base
belongs_to :category
belongs_to :categorizable, :polymorphic => true
end
car.rb
class Car < ActiveRecord::Base
has_many :categorizings, :as => :categorizable, inverse_of: :car, dependent: :destroy
has_many :categories, through: :categorizings
end
vendor.rb
class Vendor < ActiveRecord::Base
has_many :categorizings, :as => :categorizable, inverse_of: :vendor, dependent: :destroy
has_many :categories, through: :categorizings
end
cars_controller.rb
class CarsController < ApplicationController
def new
#car = Car.new
end
def create
#car = current_user.cars.build(car_params)
if #car.save
redirect_to #car
else
render 'new'
end
end
private
def car_params
params.require(:car).permit(:name, :details, :type, :category_ids => [] )
end
end
schema.rb
create_table "categories", force: :cascade do |t|
t.string "name"
t.datetime "created_at"
t.datetime "updated_at"
end
create_table "categorizings", force: :cascade do |t|
t.integer "category_id"
t.integer "categorizable_id"
t.string "categorizable_type"
t.datetime "created_at"
t.datetime "updated_at"
end
add_index "categorizings", ["categorizable_type", "categorizable_id"], name: "index_categorizings_on_categorizable_type_and_categorizable_id", using: :btree
This is what I have in the form
<%= f.collection_select :category_ids, Category.all, :id, :name %>
And I receive this error:
Unpermitted parameter: category_ids
I am very confused right now and lost in models. Dont know this is the best approach or not. I would be glad if someone could tell me where I do the mistake.

Answer 1

Using this select_tag solved my problem
<%= f.select :category_ids, Category.all.collect {|x| [x.name, x.id]}, {}, :multiple => true %>
but stops working if I disable multiple like
:multiple => false