Show HN: Finite State Machine for Go

by maxpersson • 12 years ago

6 4 12 years ago

I mostly like this. The only gripe I have with it is the stringly-typed way of triggering events. It seems like you might be able to better leverage the type system to ensure that spelling mistakes or fat-fingerings don't cause a runtime error sometime in the future. If the .Event() method took an object that satisfied the "Trigger" (or something) interface, instead of just a string, you might be able to catch those kinds of errors during compile-time instead.

maxpersson2• 12 years ago

Thanks for the feedback! It's a good suggestion, and having something else than strings as events is something that I have analyzed. Currently different handlers depends on string operations as selectors, for example "before_<event>". Any ideas on how to move that to the static type world (preferably without using the reflect package)?

lsllc• 12 years ago

I prefer to use Ragel as a DSL for FSMs, it'll generate Go code along with other languages. Adrian Thurston has done a fantastic job with Ragel.

Zed Shaw wrote a great essay about state charts in Ragel:

http://www.zedshaw.com/essays/ragel_state_charts.html

The official docs:

http://www.complang.org/ragel/ragel-guide-6.8.pdf

maxpersson2• 12 years ago

That looks really cool, awesome to be able to generate static FSM code. I use my FSM (and started to use Jake Gordon's) when I need a lightweight state variable, a step up from a collection of bools when it starts to get messy with lots of ands and ors.

Show HN: Finite State Machine for Go

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