Using Rails to build a GUI for an existing CLI Ruby script?

Question

G'day guys,

Currently having a bit of a philsophical conundrum. Myself and a few mates have built a quite awesome ruby CLI script for parsing and managing data. It uses gems, responds to requests and is fully functional and great.

I was wondering if there was any way I could hold a singleton instance of this class and interact with it via a web interface built in rails. I've got a decent amount of rails experience but can't for the life of me figure how how to create a singleton instance in a web-app and how to make that universally accessible to all of the classes/controllers.

The reason I need to create a singleton is that I need to load in a bunch of data that this little script chops and changes. It's class-based, but I don't want to port those classes over to using activerecord if I don't have to, as it keeps everything in memory (and it doesn't take up that much memory).

Is there any way I can just import the script, start it up with the requisite commands and then hold that object in memory for the life of the web application, or would I have to port over the classes/methods to AR or controller methods?

Cheers

Answer 1

You can add an initializer that contains a Singleton wrapper for your object:

config/initializers/foo_factory.rb:

require 'foo'
class FooFactory
  class << self
    def foo
      @@foo ||= Foo.new(lots, of, params)
    end
  end
end

From anywhere else you can now use:

FooFactory.foo.do_something

Note that this is extremely horrible, and you probably should not do it. However, it will do what you want: establish a global singleton that only gets set up on server start.

An even shorter hack of similar horribleness is to just assign your single Foo instance to a constant:

config/initializers/foo_singleton.rb:

require 'foo'
FooSingleton = Foo.new(lots, of, params)

Elsewhere you can then use:

FooSingleton.do_something

Note that this is basically only slightly better than a global variable in that you can't (easily) change the value of FooSingleton.