How do I solve this Devise authentication challenge? - ruby-on-rails

Question

Hello people I have some challenges here with devise authentication for users:
I have two models called color and sub_color in my application. the sub_color belongs_to color and color has_many sub_colors.I have already seeded the database with the appropriate data
The challenge; I want a user to be able to chose these in the devise form_for when they are registering as a collection object and the id of the sub_color will be used for identifying a particular user also(a situation where for instance I can sort all the users which cosed blue color). How do I achieve this please?
This is what I have tried but it is not working:
%= simple_form_for(resource, as: resource_name, url: registration_path(resource_name)) do |f| %>
<%= f.error_notification %>
<div class="form-inputs">
<%= f.input :email, required: true, autofocus: true %>
<%= f.input :user_name, required: true %>
<%= f.input :password, required: true, hint: ("# {#minimum_password_length} characters minimum" if #minimum_password_length) %>
<%= f.input :password_confirmation, required: true %>
<%= f.input :first_name, required: true %>
<%= f.label :color_id, "Color" %> <br/>
<%= f.collection_select :color_id, Color.order(:name), :id, :name, include_blank: true%>
<%= f.label :sub_color_id, "Sub Color" %> <br/>
<%= f.grouped_collection_select :sub_color_id, Color.order(:name), :sub_color, :name, :id, :name, include_blank: true%>
<div class="form-actions">
<%= f.button :submit, "Sign up" %>
</div>
model for users:
belongs_to :sub_color
has_one :color, through: :sub_color
devise.......
end
model for sub_color
has_many :users
belongs_to :color
end
model for color
has_many :sub_color
end
This is the error I see on the web browser
NoMethodError in Devise::Registrations#new
[undefined method `color_id' for #<User:0xbacc720>]

Answer 1

Firstly, You need to add color_id and sub_color_id to users table.
Then define association, in user.rb belongs_to :sub_color and in sub_color.rb has_many :users. Same goes with color, user.rb belongs_to :color and in color.rb has_many :users .
Hope that helps!