Question

I have a form and when its posted, some of its data gets saved into the database using the rails model. Along with the database, I need to store some of the content into a file. Can I enhance the “save” method in the model to write the content to the file? Is this a good design. If not what would be ideal design.

Continuing on this, I want to set the location where this file is stored, in the application configuration. Which file should I define this variable for the file location and how do I access it in the model/controller

Thanks
Kiran

Answer 1

You can of course use one of the existing, ready-made file-attachment libraries, such as paperclip and carrierwave.

Otherwise, you can:

# config/application.rb
# ...
config.my_app.cache_file_prefix = "/tmp/files"

# app/models/my_model.rb
class MyModel < ActiveRecord::Base

  # Causes ActiveRecord to run this method
  # before saving (creating or updating).
  before_save :copy_to_file

private

  def copy_to_file
    # Write data to the file.
    file_name = copy_to_file_name
    File.open(file_name) do |f|
      f.write("some data")
    end
  end

  def copy_to_file_name
    # Calculate and return the expected file name.
    prefix = Rails.configuration.my_app.cache_file_prefix
    "#{prefix}/#{id}"
  end

end

Please note that this solution will not work once you have more than one server running your Rails application. You should consider using either an object storage provider (such as S3 or Rackspace) or a replicated or distributed file system (such as DRDB or GlusterFS).