[dnautics]

You may like this: the very odd gen_statem callback pattern exists to group different callbacks by state (which you can't do because you need to group like headers together). But in Elixir, we use modules and macros to organize our code more sanely and less ad-hoc-ey:

https://hexdocs.pm/state_server/StateServer.html

[cutety]

I've only had 2 complaints with gen_statem, the docs were initially some of the most confusing/unclear and the state_functions callback mode (which I think partially is to blame for my first complaint as I was expecting a more gen_server like api with handle_* functions -- which exists but the docs use the state_functions for most of the examples and the handle_event just kinda getting some "oh by the way this exists" examples). I actually initially decided to just keep using gen_server's with a "status" or whatever value in their state as I figured it was good enough. At some point over the next few weeks I actually ended up having this talk[1] pop up in the recommend videos, and I figured I give it a watch to see if it would help make sense of gen_statem or at least just confirm that I don't need it. And while watching it, once he started explaining actions (timeouts, state_timeouts, postponing, etc) I realized that gen_statem literally solves so many problems that I've had in the back of my mind on the project I was working on like "I should figure out a way to change the state of A and do something when it doesn't receive any messages from X,Y,Z processes" (gen_statem's timeouts!) or "how should I handle messages received while attempting to recover, I guess I could put them in a queue or something..." (oh, gen_statem will let me postpone them until it's healthy!). It took a couple more re-readthroughs of the docs to fully grasp, but now it gets included in almost everything I work on, it's so useful (though I guess I should've assumed those were already solved problems by the BEAM/OTP as usual).

However, now my biggest complaint about Elixir is that gen_statem didn't get any official wrapper. StateServer looks like almost exactly what I would want out of an official Elixir wrapper. I also like to see the addition of `handle_continue` as well, because the first thing I did before migrating any of the gen_server's to gen_statem's was create a small wrapper module to a) make the handle_* return values more in like with GenServer's (basically just making it {:(no)reply, (transition|keep), data, [actions]}) and b) add a quick and dirty handle_continue callback because I use it all the time with GenServer. And this literally just looks like a more polished version of that, so thanks!

[1] https://www.youtube.com/watch?v=_4MTIffWhYI