I want to write a gem, how do I make it such that I have a variable / method accessible to all views, models, and controllers?

I want to write something that can be accessible from all parts of the MVC structure. But I haven't the slightest idea where to begin with making methods public to each of the M, V, and C.

I found this: http://asciicasts.com/episodes/135-making-a-gem But it is super开发者_开发技巧 basic.