adding nested attributes with checkboxes in rails 4 using mass assignment

error:

expected Array (got Rack::Utils::KeySpaceConstrainedParams) for param `car'

I am making a form where I can add nested attributes to a parent record and I want to add them through checkboxes. I have the parent model "Car" and the child model "Colors"…but I want to start with some default "colors"…so I also have the model "Sample_Colors", which changes based on the "Car_Models".

I am trying to add multiple "Colors" to an associated "Car" using checkboxes…I do NOT want a HABTM relationship with "Sample_Colors" and "Colors", as I need the "Colors" record to be editable and not just a join table. I have done this using HABTM, and so I don't really understand why I can't create a non-join-table record in a similar way.

To make the mass assignment work, I've been looking at this question: How to submit multiple NEW items via Rails 3.2 mass-assignment

The checkboxes need to
1. Create a new "Color" Record (@color.new) that is associated with the @car record parent
2. Set the "text" column of the @color.new record to the sample_color.text value
3. Set the "gloss" column of the @color.new record to the sample_color.gloss value

4. The amount of checkboxes that are created == the @sample_colors that are iterated.

I built a paired down sample app to show more clearly: http://ift.tt/1GuxVWx

car_model.rb

class CarModel
has_many :sample_colors, dependent: :destroy
has_many :cars, dependent: :destroy

car.rb

class Car   
has_many :colors, dependent: :destroy
belongs_to :car_model

sample_color.rb

class SampleColor
belongs_to :car_model

color.rb

class Color
belongs_to :car

_form (for adding colors)

<%= form_for @car do |f| %>

    <%= f.fields_for 'car[color_attributes][]', @color, index: nil do |f| %>

      <label class="form-label dk-aqua">Colors for <%= @car.car_name %></label>   <br>
      <div class="row ">
       <%= hidden_field_tag "car[color_ids][]", nil %>
       <% @sample_colors.each do |sample_color| %>
         <%= check_box_tag "car[color_ids][]", "#{sample_color.id}"  %>  
         <%= hidden_field_tag "car[]", "#{sample_color.text}" %> 
         <%= hidden_field_tag "car[color_glosses][]", "#{sample_color.gloss}" %> 
         <%= label_tag "car[color_texts]", "#{sample_color.text}" %>  <br>
       <% end %>
     </div>
    <%end%>

        <%= f.submit 'SAVE CHANGES',  :class => 'btn btn-green btn-lg btn-block' %>  
    <%end%>

cars_controller.rb

  def update
    @color = Color.new(color_params)
    @car.color_ids = params[:car][:color_ids] || []
    @car.color_texts = params[:car][:color_texts] || []
    @car.color_glosses = params[:car][:color_glosses] || []
        respond_to do |format|
      if @car.update(car_params)
        format.html { redirect_to @car, notice: 'Car was successfully updated.' }
        format.json { render :show, status: :ok, location: @car }
      else
        format.html { render :edit }
        format.json { render json: @car.errors, status: :unprocessable_entity }
      end
    end
  end

def car_params
      params.require(:car).permit(:id, :car_name, :car_model_id, colors_attributes: [:id,  {:color_ids => [], :color_texts => [], :color_glosses => []},  :text, :gloss]  )
    end

    def color_params
      params.require(:color).permit(:id, :text, :gloss, {:color_ids => [], :color_texts => [], :color_glosses => []},  )
    end