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I wrote up a short blurb on how to get quick IoC in a sketch on here: http://jestermax.wordpress.com/2014/03/14/quick-and-accessible-inversion-of-control/
It requires setting up PicoContainer in your Library folder. It covers just a basic usage and some examples of how you could use it and what it could gain you in the long run.
Comments
A bit advanced for the general audience of Processing, but it is good to have an introduction to the concept here, and it presents good, solid ideas.
BTW, I moved the topic, How To is more about asking questions.