[erlang-questions] Deriving records from one another?

[Ulf Wiger]

It sounds to me that you are trying to model multiple state machines inside one process. If I’m wrong about this, you may skip the rest of this mail. ;-)

I talked about a similar problem in this presentation http://vimeo.com/8672652 (Øredev 2009), ca 44 minutes into the presentation (41 - 44 minutes might also be interesting to listen to, depending on how used you are to the Erlang style).

I recall encountering this issue in ‘industrial programmers’, where they model processes as they are used to from C programming. Splitting processes into multiple state machines can then simplify the code greatly and also make it both faster and more robust.

BR,
Ulf W

On 23 Jun 2014, at 15:49, Roger Lipscombe <roger@REDACTED> wrote:

> I'm probably thinking too OO by calling it "deriving", but here's the problem:
> 
> OTP handlers (gen_server, etc.) take a State parameter. You can stick
> anything in here, but generally I've been using a #state record, and
> keeping a bunch of values in it.
> 
> Now I'd like to actually start representing *state* with the State[1].
> That is, I'd like to be able to match on #init, #ready,
> #expecting_key, #whatever records. This will hopefully make the code
> easier to read, and means that my record doesn't have to contain
> fields for stuff that's not relevant in the given state.
> 
> ...
> 
> Cheers,
> Roger.
> 
> [1] No, I don't think that gen_fsm is the answer at this point.
> Interesting suggestion, though, thanks.
> [2] Still on R16, so I can't use maps, but I'm still interested in how
> they might help, if at all.
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Ulf Wiger, Co-founder & Developer Advocate, Feuerlabs Inc.
http://feuerlabs.com