[erlang-questions] code_change for gen_fsm: how to actually handle a state change

Barco You <>
Tue Nov 22 07:52:22 CET 2011


What you mean is like this?

code_change(_OldVer, Statename, Data = #state{}, _Extra) ->
         {ok, Statename, Data#state{ newfield = Something}.



On Tue, Nov 22, 2011 at 2:38 PM, Bengt Kleberg
<>wrote:

> Greetings,
>
> The way it is done in our code (lots of it) is to match the old record
> as a tuple.
>
>
> bengt
>
> On Mon, 2011-11-21 at 16:51 +0100, Daniel Dormont wrote:
> > Hello all,
> >
> > I have a gen_fsm module and would like to take advantage of hot code
> > deploy. The module uses a record (called "state") and the new version
> > of the module includes some new fields in the record. What is a nice
> > clean way to code the my_module:code_change function to deal with
> > this? Are there any good examples out there on the web?
> >
> > Note: for my purposes it would be sufficient to detect that the state
> > record is out of date, and terminate cleanly. BUT the correct
> > functionality of the terminate/3 function in my module depends on the
> > state data, and I would need it to complete cleanly and not crash in
> > this instance because there are other processes that depend on this
> > one and need to be notified properly of its exit. The issue is that
> > the state itself contains the data of which processes those are.
> >
> > What's the best approach here?
> >
> > thanks,
> > Dan
> > _______________________________________________
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> > 
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>
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