Rails and has_many through association - how to properly set the form?

Question

I am not sure I am setting my models correctly, so I would like to show you my idea:

I have the model Car that belongs to Company . Then I have a model called Color . In this DB table are stored all colors (red, blue, ...). And then there is the 4th model, called CarColor . This model contains two columns - job_id and color_id .

In the view, I would like to allow visitors to pick out colours with using checkboxes.

Form partial

= form_for @car do |f|
  .field
    = f.label :name
    = f.text_field :name
  .field
    = f.label :location
    = f.text_field :location
  .field
    = fields_for @car_colors do |cc|
      ...
  .field
    = fields_for @company do |c|
      .field
        = c.label :name
        = c.text_field :name

  .actions
    = f.submit 'Save'

Models

class Company < ActiveRecord::Base
  has_many :cars
end
class Car < ActiveRecord::Base
  belongs_to :company

  has_many :car_colors
  has_many :c_colors, :through => :car_colors
end
class Color < ActiveRecord::Base 
  has_many :car_colors
  has_many :cars, :through => :car_colors
end
class CarColor < ActiveRecord::Base
  belongs_to :car
  belongs_to :color
end

Saving Cars + Company works well, but I don't know how to add the checkboxes with colours in the view.

EDIT: Regarding to the thread in the comment, I made a progress. However, I found an error that I don't know how to solve.

I am using model structure shown above and this is how look like the view:

- Color.order('name').each do |clr|
  = check_box_tag :c_color_ids, clr.id, @car.car_colors.include?(clr), :name => 'car[c_color_ids][]'
  = label_tag :c_color_ids, clr.name

This is the error I got:

PG::Error: ERROR:  relation "car_colors" does not exist

What am I missing? How the relation cannot exist?

Answer 1

Ok, I spent a day of solving this issue. The scheme about is correct, the problem in my case was, that I have create a migration with table name car_color instead of car_colors ...