undefined method `class_detail' for nil:NilClass - ruby-on-rails

Question

I have two tables class_details and user_classes. user_classes table is dependent of user table and class_details and class_details is independent of user table. Now my requirement is that when i click a button few details must be saved to the database which belong to different tables. User dependent table are only getting saved to database and not the user independent tables and i am getting error undefined method class_detail for nil:NilClass
Controller code
def update_profile
if #user.update(user_params)
redirect_to profile_index_path, notice: 'Profile was successfully updated.'
else
render :index
end
end
end
private
def set_user
#user = User.find(current_user.id)
#user.fee || #user.build_fee
#user.user_class || #user.build_user_class
end
def user_params
params.require(:user).permit(:name, fee_attributes: %i[id fee_hour fee_month], user_class_attributes: %i[id class_detail [id class_name class_category]])
end
class_detail.rb
class ClassDetail < ApplicationRecord
has_one :user_class, dependent: :destroy
end
user_class.rb
class UserClass < ApplicationRecord
belongs_to :user
belongs_to :class_details
validates_presence_of :user_id
end
user.rb
has_one :fee, dependent: :destroy
accepts_nested_attributes_for :fee
has_one :user_class, dependent: :destroy
view code
<%= form_for(#user, url: {action: 'update_profile'}, html: {class: 'm-form m-form--fit m-form--label-align-right'}) do |f| %>
<%= f.fields_for :fee, #user.fee do |u| %>
<%= u.number_field :fee_hour, class: 'form-control m-input', placeholder: t('.fee_for_hour') %>
<% end %>
<%= f.fields_for :user_class, #user.user_class do |k| %>
<%= f.fields_for :class_detail, #user_class.class_detail do |c| %>
<%= c.text_field :class_name, class: 'form-control m-input' %>
<% end %>
<% end %>
Can anyone help me updating user independent table! Thank you in advance

Answer 1

params.require(:user).permit(:name, fee_attributes: %i[id fee_hour fee_month], user_class_attributes: %i[id class_detail [id class_name class_category]])
That means you want to update class_detail from user_class, but you need to define nested attributes:
class UserClass < ApplicationRecord
belongs_to :user
belongs_to :class_details
accepts_nested_attributes_for :class_details, update_only: true
validates_presence_of :user_id
end
Also, the form must look like this:
<%= form_for(#user, url: {action: 'update_profile'}, html: {class: 'm-form m-form--fit m-form--label-align-right'}) do |f| %>
<%= f.fields_for :fee, #user.fee do |u| %>
<%= u.number_field :fee_hour, class: 'form-control m-input', placeholder: t('.fee_for_hour') %>
<% end %>
<%= f.fields_for :user_class, #user.user_class do |k| %>
<%= k.fields_for :class_detail, #user.user_class.class_detail do |c| %>
<%= c.text_field :class_name, class: 'form-control m-input' %>
<% end %>
<% end %>
<% end %>
And in your controller:
def user_params
params.require(:user).permit(:name, fee_attributes: %i[id fee_hour fee_month], user_class_attributes: [:id, { class_detail: %i[class_name class_category] }])
end
Edited:
That all means class_details and user_class are associated to the user already. Build references model - child-child-model - child-parent-model from the single call not possible. You can build this references in the edit action. For example:
def edit
#user.create_user_class!(class_detail: ClassDetail.find(n)) unless #user.user_class
end