caboose

This is a fancy one for you dry-configuration-heads out there. First up, lets say you're storing digital assets in a rails app, and you want the user to enter what sort of content-type it is: image, video, html, whatever, when (before) they upload the file. So, you want to fill in a text-box with a suitable default after they select the file on their system. And, to make matters more interesting, you want to use the same regex on the filename on the server-side as you do on the client-side. First up, let's assume that the extension of the file is, indeed, indicative of the content-type. So, open up environment.rb (gasp!) and make yourself a configuration module for your app. Please note, if you have a better way of doing this, let me know; I'm too busy to trawl Martin Fowler's bliki for the correct pattern here, people! Please note, some highly questionable ruby code follows. (I wrote this as a module because I don't really want to instantiate the config object. Again, feel free to correct me. Also, I'm defining these values in methods, because I have some more that actually take arguments.)

module MyApp
  module Config
    class << self
      #define a bunch of regexes
      def image_tags
        /jpg|gif|png|tif|eps/
      end
      def document_tags
        /pdf|doc|xls|txt/
      end
      def movie_tags
        /mov|qt|qt3/
      end
    end
  end
end

In your view, you want something like this: (make sure it's multipart!)

Some explanation: - I bind the element_file to that anonymous function so I can use 'this'. Just 'coz I love that little sucker. - We iterate over all the class (singleton) methods in Config; you may like to subclass it further, like Config::ContentTypes or something. - I use 'inspect' so it gives a JS-happy regex This allows us to use the same regexes on server and client-side. Possible changes: - use instance variables, or something - use JSON - use Behavior