My Model

gistfile1.rb

class Choice < ActiveRecord::Base
  
  # Environment-specific direct upload url verifier screens for malicious posted upload locations.
  DIRECT_UPLOAD_URL_FORMAT = %r{\Ahttps:\/\/s3\.amazonaws\.com\/mybucket\/(?<path>uploads\/.+\/(?<filename>.+))\z}.freeze
  
  has_many :template_assignments
  has_many :templates, :through => :template_assignments
    
  # This method associates the attribute ":picture" with a file attachment
    has_attached_file :picture, styles: {
      thumb: '300x200>',
      square: '200x200>',
      large: '500x500>'
    }

    validates :direct_upload_url, presence: true, format: { with: DIRECT_UPLOAD_URL_FORMAT }

    before_create :set_upload_attributes
    after_create :queue_processing
  
    # Store an unescaped version of the escaped URL that Amazon returns from direct upload.
    def direct_upload_url=(escaped_url)
      write_attribute(:direct_upload_url, (CGI.unescape(escaped_url) rescue nil))
    end
    
    # Determines if file requires post-processing (image resizing, etc)
    def post_process_required?
      %r{^(image|(x-)?application)/(bmp|gif|jpeg|jpg|pjpeg|png|x-png)$}.match(upload_content_type).present?
    end
  
    # Final upload processing step
    def self.transfer_and_cleanup(id)
      choice = Choice.find(id)
      direct_upload_url_data = DIRECT_UPLOAD_URL_FORMAT.match(choice.direct_upload_url)
      s3 = AWS::S3.new
    
      if choice.post_process_required?
        choice.upload = URI.parse(URI.escape(chioce.direct_upload_url))
      else
        paperclip_file_path = "documents/uploads/#{id}/original/#{direct_upload_url_data[:filename]}"
        s3.buckets[Rails.configuration.aws[:bucket]].objects[paperclip_file_path].copy_from(direct_upload_url_data[:path])
      end
 
      choice.processed = true
      choice.save
    
      s3.buckets[Rails.configuration.aws[:bucket]].objects[direct_upload_url_data[:path]].delete
    end
      
    protected
  
    # Set attachment attributes from the direct upload
    # @note Retry logic handles S3 "eventual consistency" lag.
    def set_upload_attributes
      tries ||= 5
      direct_upload_url_data = DIRECT_UPLOAD_URL_FORMAT.match(direct_upload_url)
      s3 = AWS::S3.new
      direct_upload_head = s3.buckets[Rails.configuration.aws[:bucket]].objects[direct_upload_url_data[:path]].head
 
      self.upload_file_name     = direct_upload_url_data[:filename]
      self.upload_file_size     = direct_upload_head.content_length
      self.upload_content_type  = direct_upload_head.content_type
      self.upload_updated_at    = direct_upload_head.last_modified
    rescue AWS::S3::Errors::NoSuchKey => e
      tries -= 1
      if tries > 0
        sleep(3)
        retry
      else
        false
      end
    end
  
    # Queue file processing
    def queue_processing
      Choice.delay.transfer_and_cleanup(id)
    end
end