Re: [Boost-users] signals/slots and boost::functions

Subject: Re: [Boost-users] signals/slots and boost::functions
From: david.weber_at_[hidden]
Date: 2008-12-10 16:10:07

I suppose that it's good to back up a bit, and discuss that to make sure
I'm at least on the right track.

I have an object which will signal when something interesting occurs.
(Signaller)

I want other "interested" objects to receive this signal when that
"interesting thing" occurs. (Slotter)

We wanted to encapsulate the signal.connect(&slot) calls within the
Signaller and then the Slotter just hooks up whatever function they want
(provided it matches the function signature).  Now, the slots are most
likely going to be instance member functions, which according to my
research, and my own testing, is easiest done with boost::bind.

So, the Signaller has a connect(&slot) function, that returns success or
not.  It didn't seem "natural" for the Slotter to have to keep &
maintain his connection object for eventual disconnection of the signal.
So a disconnect(&slot) function was added to the Signaller class.

We want to be as robust as possible, and our use case doesn't allow the
same slot to be connected to a signal multiple times, so this (and
several other reasons) are why we are looking at maintaining this stl
map separately.

I'm going from memory at this point, but I believe the reason we call
connection.disconnect() versus signal.disconnect(&slot), is in our
Signaller.disconnect(&slot), the Slotter didn't necessarily maintain
their own bind object permanently.  For simple cases, you don't even
need the bind object at all.  If I go from memory, it was creating a new
bind object every single time, and you couldn't disconnect properly.

Let me dig up that code again, see if I can remember why I decided to go
this route.  It's obviously a bit complicated, and I would love to
alleviate the connection management from the Signaller class
alltogether.

--dw

> -----Original Message-----
> From: boost-users-bounces_at_[hidden] 
> [mailto:boost-users-bounces_at_[hidden]] On Behalf Of 
> Frank Mori Hess
> Sent: Wednesday, December 10, 2008 2:48 PM
> To: boost-users_at_[hidden]
> Subject: Re: [Boost-users] signals/slots and boost::functions
> 
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> On Wednesday 10 December 2008 14:45 pm, david.weber_at_[hidden] wrote:
> > Part of the management, is I need to map the function 
> pointer to the 
> > actual connection object.
> 
> I'm curious to hear more about your use case.  The signal 
> class supports disconnect-by-slot, did you need the 
> connection object for something other than just 
> disconnecting?  It would seem possible to generalize 
> disconnect-by-slot into a more general method which returns a 
> list of connections whose slot or group is equal to the 
> method's argument.
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