Question

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)

Answer 1

If you look on http://apidock.com/rails/ActiveRecord/NestedAttributes/ClassMethods/accepts_nested_attributes_for you’ll see that accepts_nested_attributes_for only exists since Rails 2.3.2, so I’m afraid you won’t have that functionality if you’re running off of 2.2.