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

Barco You <>
Tue Nov 22 08:27:37 CET 2011


But I don't think it's much different from directly matching the record
itself as shown by my previous mail.


Barco

On Tue, Nov 22, 2011 at 3:24 PM, Bengt Kleberg
<>wrote:

> The old record is a tuple. Like this:
>
> code_change(_Old_version, State_name, {state, Item1, Item2}, _Extra ) ->
>        {ok, State_name, Data#state{item1=Item1, item2=Item2,
> newfield=something}.
>
>
> bengt
>
> On Tue, 2011-11-22 at 07:52 +0100, Barco You wrote:
> > 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 record is out of date, and terminate cleanly.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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