Question

I have a Subject Model and a Lesson Model.
I implemented a nested model form.

After subject creation, I led it to a page where it supposedly shows the lessons associated. However, I fail to see the lessons.

I believe the data for lessons did not get saved properly as
When I did a for example lesson.find_by_subject_id(‘1’), I get ‘nil’ in return.

I am trying to figure out how polymorphism works on rails and would appreciate it if someone could either point out where I’ve gone wrong or give me some guidance on how those to pass the values for belong_to classes to be created.

Subject Model

attr_accessible :subjectCode, :lessons_attributes
has_many :lessons, :dependent => :destroy
accepts_nested_attributes_for :lessons, :reject_if => lambda { |a| a[:content].blank? }, :allow_destroy => true

Lesson Model

attr_accessible :lessonName, :subject, :subject_id
belongs_to :subject

Subject Controller

def new
3.times {@subject.lessons.build}
end

def create
  @subject = Subject.new(params[:subject])
  if @subject.save
    redirect_to @subject, :notice => "Successfully created subject."
  else
    render :action => 'new'
  end
end

Form

<%= form_for @subject do |f| %>
  <%= f.error_messages %>
  <p>
    <%= f.label :subjectCode %><br />
    <%= f.text_field :subjectCode %>
  </p>

  <%= f.fields_for :lessons do |builder| %>
    <p>    
    <%= builder.label :lessonName %> <br/>
    <%= builder.text_area :lessonName, :rows=>3 %>
    </p>
  <% end %>
  <p><%= f.submit "Submit" %></p>
<% end %>

Routes
resources :subjects do resources :lessons end

Answer 1

Your reject_if lambda will always reject the lessons attributes because lessons don’t have a content attribute, so you’re essentially evaluating nil.blank? which will return true

Perhaps you want to check if the lesson name is blank? Ala :reject_if => lambda { |a| a[:lessonName].blank? }