job.rb

$ cat job.rb
class Job < ActiveRecord::Base
  attr_accessor :file_data

  before_validation :read_file
  after_create :copy_file

  validates :filename, :presence => true
  validates_format_of :filename, :with => %r{\.foo$}i, :if => "!filename.nil?", :message => "lorem ipsum"

  def real_path
    "#{Rails.root}/public/uploads/foo/job_#{self.id}#{File.extname(self.filename)}"
  end

  def update_status!(status, observations = '')
    self.status = status
    self.observations = observations
    self.save
  end

 private
  def read_file
    return if self.file_data.nil?

    input = self.file_data
    self.filename = input.original_filename
    #self.content_type = input.content_type.chomp
    #self.size = input.size
  end

  def copy_file
    return if self.file_data.nil?

    input = self.file_data

    file_path = real_path
    dir_path = File.dirname(file_path)
    FileUtils.makedirs(dir_path)   if !File.exist?(dir_path)
    File.open(file_path, "wb"){ |f| f.write(input.read) }
  end