Implementing the State Machine Pattern as a Stream Processor

In my last blog, I said that I really thought that some of the Gang Of Four (GOF) patterns were becoming somewhat obsolete, and if not obsolete then certainly unpopular. In particular I said that StateMachine wasn’t that useful as you can usually think of another, simpler way of doing whatever it is you’re doing rather than using it. In order to make amends, both for preaching obsolescence and for the hideous ‘C’ code that I attached to the end of my last blog, I thought that I’d demonstrate the use of StateMachine in converting Twitter tweets into HTML.

The Importance of Questioning

One of the comments my about my last blog Design Patterns, The Emperor’s New Clothes and Catch 22 was that “one of the most valuable things these patterns offer is vocabulary. They give something a name.”, which is an important point that I think I missed. The idea is that once something has a name then it’s something you can easily communicate about. For example, it’s easier to say “I’ve used a Singleton” rather than “I’ve created this class where there’s only ever one instance and that instance is available to all other classes in the application”

Design Patterns, The Emperor’s New Clothes and Catch 22

When writing this blog one of the things I do before I metaphorically put pen to paper is to verify what I’m going to write is correct and I usually do that by either checking a text book or looking on the Internet. Now, my last blog described the Strategy Pattern and, of course I double checked that I wasn’t presenting the Bridge Pattern which has a UML diagram that’s very similarl to Strategy. In doing this it occurred to me that the Gang Of Four (GOF) design patterns have been around a few years (again I double checked Design Patterns: Elements of ReusableObject-Oriented Software by the Gang of Four: Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides was first published in 1994) and that over the years these ideas have been copied and republished in numerous blogs and on a multitude of web sites. It then occurred to me that if these patterns have been around for such a long time, then why is it that they aren’t that well known and more widely used on a daily basis?