How to modify a Rails engine to require my library?

I have a Rails engine (someone else's gem) that I am trying to modify by adding another gem as a dependency. I can't seem to f开发者_高级运维igure out how to get the engine to require the library. I've tried all sorts of different things, but I can't seem to get it to work.

My main app Gemfile I have the engine:

gem 'enginegem'

In the engine's gemspec I have:

s.add_dependency 'somethinggem', '~> 1.0'

In the Engine, there is a model that I am trying to modify by adding this acts_as_something method:

class Page < ActiveRecord::Base
  acts_as_something
end

And there is a controller that I am trying to modify:

class PagesController < ApplicationController
  around_filter :do_something

  def do_something
    my_var = 'foobar'
    Something.do_something_with my_var do
      yield
    end
  end
end

What is the appropriate way to add this library as a dependency to the engine and have it require the library?

---

It'd help if you told us which gem you're trying to modify.

In most gems you will have a lib/enginegem.rb, there is probably the best place to require the gem:

require 'somethinggem'

EDIT: Although this answer didn't help the OP (see comments below), I'll keep it here, because it may help others.

EDIT 2: Everybody who is trying to create an engine should take a look at devise's code. If you want a more didactic approach, try Crafting Rails Applications book from Jose Valim. In fact, if you're serious with this engine, you should do both.