Subject: Re: [Boost-users] [signals (thread safe)] Scope of slot_call_iterator (or how to implement deferred signals)
From: Frank Mori Hess (fmhess_at_[hidden])
Date: 2009-02-03 20:26:14
On Tuesday 03 February 2009 18:15, Fabio Fracassi wrote:
> I am currently trying to implement deferred signals using boost signals
> (well thread safe signals). I had the (crazy?) idea that it might be
> possible to hijack the combiner interface to do this.
>
> The design rational said that during the signal call the state
> (including the arguments that were passed) are cached for the combiner.
> So, what I tried to do was to copy and store the first and last iterater
> out of the combiner, to iterate over them at a later time, to call the
> slots. What I don't know is whether the slot_call_iterator (and the data
> it uses ) stays in scope after the signal call (i.e.
> signal...::operator() ) returns.
It's definitely not safe to do that with the current implementation, it's
not a usage I've considered before. It does seem like it would be
possible for the library to support what you want to do, adding a feature
to the slot call iterators similar to what
boost::shared_container_iterator provides. My current priority is to
actually get the library into a release over adding new features though.
My expectation was that someone doing what you are trying to do would
bundle up the arguments on their own in their slot, to send them off to
wherever. It does seem like it could be a convenience to let them copy
the slot call iterators out of the scope of the signal invocation, since
the signal has already internally bundled the arguments.