undefined method `new_record?' for nil:NilClass-Collection of common programming errors

In rails 3.2 I created a post controller. Each post can have a different number of paperclip attachments. To achieve this I created a assets model where each asset has a paperclip attachment. One post has_many assets and assets belong_to post.

Asset model

class Asset < ActiveRecord::Base
    belongs_to :post
    has_attached_file :photo, :styles => { :thumb => "200x200>" }
end

Post model

 class Post < ActiveRecord::Base
      attr_accessible :content, :title
      has_many :assets, :dependent => :destroy
      validates_associated :assets
      after_update :save_assets

 def new_asset_attributes=(asset_attributes) 
        asset_attributes.each do |attributes| 
            assets.build(attributes) 
        end 
    end
    def existing_asset_attributes=(asset_attributes) 
        assets.reject(&:new_record?).each do |asset| 
        attributes = asset_attributes[asset.id.to_s] 
        if attributes 
            asset.attributes = attributes 
            else 
                asset.delete(asset) 
            end 
        end 
    end

    def save_assets 
        assets.each do |asset| 
            asset.save(false) 
        end 
    end 
end

Posts helper

module PostsHelper
  def add_asset_link(name) 
    link_to_function name do |post| 
      post.insert_html :bottom, :assets, :partial => 'asset', :object => Asset.new 
    end 
  end
end

Form for post

 { :multipart => true } do |f| %>
  
    
      

prohibited this post from being saved:

    
  

  
    

    
  
  
    

    
  
    
        Attach a file or image

         @post.assets %> 
       
  
    
  

Asset partial

 
    
    

     
        
 
          Asset:  
           
        

 
   

Most of the code is taken from here: https://gist.github.com/33011 and I understand this is a rails2 app, anyway I don’t understand what this error means:

undefined method `new_record?' for nil:NilClass
Extracted source (around line #2):

1:  
2:     
3:     
4:     
5:      

1. Try changing this

    
       Attach a file or image
   
        @post.assets %> 
     
   

   to

   
     Attach a file or image
   
     
        asset %> 
     
   
   

   Possible reason is when u calling

    @post.assets %> 
   

   You are passing a collection to the rendered partial but you are no where using ur collection passed by the name collection in the partial. you are using a variable Assest which doesnt exist in scope of that particular rendered partial 🙂

2. Reading the error, your @post.assets %> line calls an empty array maybe? In your console, can you find @post.assets and is it nil there?

Originally posted 2013-11-09 21:05:57.