This will probably just be a simple problem and I am just blind or an
idiot but I could use some help.
So I am going over some basic guides in Rails, reviewing the basics
and such for an upcoming exam.  One of the guides included was the
sort-of-standard getting started guide over at guide.rubyonrails.org.
Here is the link if you need it.  Also all my code is for my app is
from there, so I have no problem releasing any of my code since it
should be the same as shown there.  I didn't do a copy paste, but I
basically was typing with Vim in one half of my screen and the web
page in the other half, typing what I see.
http://guides.rubyonrails.org/getting_started.html
So like I said, I am going along the guide when I noticed past a
certain point in the tutorial, I was always getting an error on the
site.  To find the section of code, just hit Ctrl+f on the page (or
whatever you have search/find set to) and enter "accepts_".  This
should immediately direct you to this chunk of code.
class Post < ActiveRecord::Base
  validates_presence_of :name, :title
  validates_length_of :title, :minimum => 5
  has_many :comments
  has_many :tags
  accepts_nested_attributes_for :tags, :allow_destroy => :true  ,
   :reject_if => proc { |attrs| attrs.all? { |k, v| v.blank? } }
end
So I tried putting this in my code.  It is in
~/Rails/blog/app/models/post.rb in case you are wondering.  However,
even after all the other code I put in past that in the guide, hoping
I was just missing some line of code that would come up later in the
guide.  But nothing, same error every time.  This is what I get.
  NoMethodError in PostsController#index
  
  undefined method `accepts_nested_attributes_for' for #<Class:0xb7109f98>
  
  /usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/base.rb:1833:in
  `method_missing'
  app/models/post.rb:7
  app/controllers/posts_controller.rb:9:in `index'
  
  Request
  
  Parameters:
  
  None
  
  Response
  
  Headers:
  
  {"Content-Type"=>"",
   "cookie"=>[],
   "Cache-Control"=>"no-cache"}
Now, I copied the above code from the guide.  The two code sections I
edited mentioned in the error message I will paste as is below.
class PostsController < ApplicationController
  # GET /posts
  # GET /posts.xml
  before_filter :find_post,
    :only => [:show, :edit, :update, :destroy]
  def index
    @posts = Post.find(:all) # <= the line 9 referred to in error message
    respond_to do |format|
      format.html # index.html.erb
      format.xml  { render :xml => @posts }
    end
  end
class Post < ActiveRecord::Base
  validates_presence_of :name, :title
  validates_length_of :title, :minimum => 5
  has_many :comments
  has_many :tags
  accepts_nested_attributes_for :tags, :allow_destroy => :true  , # <= problem
    :reject_if => proc { |attrs| attrs.all? { |k, v| v.blank? } }
end
Also here is gem local gem list.  I do note that they are a bit out of date, but the default Rails install any of the school machines (an environment likely for my exam) is basically 'gem install rails --version 2.2.2' and since they are windows machines, they come with all the normal windows ruby gems that comes with the ruby installer.  However, I am running this off a Debian virtual machine of mine, but trying to set it up similarly and I figured the windows ruby gems wouldn't change anything in Rails.
*** LOCAL GEMS ***
actionmailer (2.2.2)
actionpack (2.2.2)
activerecord (2.2.2)
activeresource (2.2.2)
activesupport (2.2.2)
gem_plugin (0.2.3)
hpricot (0.8.2)
linecache (0.43)
log4r (1.1.7)
ptools (1.1.9)
rack (1.1.0)
rails (2.2.2)
rake (0.8.7)
sqlite3-ruby (1.2.3)
So any ideas on what the problem is?  Thanks in advanced.