NoMethodError Building a simple CMS in Rails - ruby-on-rails

Question

I've been following along with this tutorial from lynda.com.
I'm in chapter 15: Nesting pages in subjects
So I've followed through and have even resorted to just copying the exercise files they provide you with. However I keep getting this error:
NoMethodError in PagesController#new
undefined method `id' for nil:NilClass
It hi-lights the second line:
def new
#page = Page.new({:subject_id => #subject.id, :name => "Default"})
#subjects = Subject.order('position ASC')
#page_count = Page.count + 1
end
Here's my controller
class PagesController < ApplicationController
layout "admin"
before_action :confirm_logged_in
before_action :find_subject
def index
# #pages = Page.where(:subject_id => #subject.id).sorted
#pages = #subject.pages.sorted
end
def show
#page = Page.find(params[:id])
end
def new
#page = Page.new({:subject_id => #subject.id, :name => "Default"})
#subjects = Subject.order('position ASC')
#page_count = Page.count + 1
end
def create
#page = Page.new(page_params)
if #page.save
flash[:notice] = "Page created successfully"
redirect_to(:action => 'index', :subject_id => #subject_id)
else
#subjects = Subject.order('position ASC')
#page_count = Page.count + 1
render('new')
end
end
def edit
#page = Page.find(params[:id])
#subjects = Subject.order('position ASC')
#page_count = Page.count
end
def update
# Find an existing object using form parameters
#page = Page.find(params[:id])
# Update the object
if #page.update_attributes(page_params)
# If update succeeds, redirect to the index action
flash[:notice] = "Page updated successfully"
redirect_to(:action => 'show', :id => #page.id, :subject_id => #subject_id)
else
# If the update fails, redisplay the form so user can fix problems
#subjects = Subject.order('position ASC')
#page_count = Page.count
render('edit')
end
end
def delete
#page = Page.find(params[:id])
end
def destroy
page = Page.find(params[:id]).destroy
flash[:notice] = "Page '#{page.name}' destroyed successfully"
redirect_to(:action => 'index', :subject_id => #subject_id)
end
private
def page_params
# Same as using "params[:subject]", except that it:
# - raises as error if :subject is not present
# - allows listed attributes to be mass-assigned
params.require(:page).permit(:subject_id, :name, :permalink, :position, :visible)
end
def find_subject
if params[:subject_id]
#subject = Subject.find(params[:subject_id])
end
end
end
Then here's the view:
<% #page_title = "New Page" %>
<%= link_to("<< Back to list", {:action => 'index', :subject_id => #subject_id}, :class => 'back-link') %>
<div class="pages new">
<h2>Create Page</h2>
<%= form_for(:page, :url => {:action => 'create', :subject_id => #subject_id}) do |f| %>
<%= render(:partial => "form", :locals => {:f => f}) %>
<div class="form-buttons">
<%= submit_tag("Create page") %>
</div>
<% end %>
</div>
A question similar to this one has been asked here, but I don't see any solutions there.
Any help is greatly appreciated!

Answer 1

I think the problem is in
Page.new({:subject_id => #subject.id, :name => "Default"})
#subject is not defined and you are asking for its id

Answer 2

You have to define #subject.
Put this as first line in your new action
#subject = Subject.find(params[:id])
Right now #subject is undefined therefore it's nil, calling .id on nil is resulting in the error you're seeing.