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

Subject: Re: [Boost-users] signals/slots and boost::functions
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2008-12-10 15:00:35

AMDG

david.weber_at_[hidden] wrote:
>
> I have a class, where I want callers to be able to register/deregister 
> signals/slots.  They will pass in a function pointer, and we'll hook 
> it up to the signal, and manage the connection object.
>
> Part of the management, is I need to map the function pointer to the 
> actual connection object.  This is where the trouble comes in.  Since 
> a boost::function doesn't have an operator <, the simplest way is to 
> just map it to an unsigned long long, and store the raw address of the 
> underlying function.
>
> So, my connect function:
>
>
> typedef VSSP (*TargetType) ( std::string, EncodingEnum);
> typedef boost::function < VSSP ( std::string, EncodingEnum) > 
> CreateTypeFunc;
>
> bool ElementBase::connectCreateTypeSignal(const CreateTypeFunc& slot)
> {
>     LOG4CXX_DEBUG(logger_, "connectCreateTypeSignal in");
>     bool retValue = false;
>  
>     unsigned long long slotAddr = (unsigned long long)slot.target< 
> TargetType >();
>     LOG4CXX_DEBUG(logger_, "*** slotAddr = " + (boost::format("%08X") 
> % slotAddr).str());
>
> <snip>
> }
>
>
> My debug printouts, are shoing unexpected behavior.  The address that 
> I am getting from target is different every time it is called, even 
> though I'm calling with the same function (getTypeSlot).  I would 
> expect this if I was getting the address of the function object, 
> because I'm creating one implicitly through the call, but not 
> dereferencing via target(), unless I'm misunderstanding what target() 
> does. 
>

target returns a pointer to the function object.  If TargetType is 
void(*)() target
will return an object of type void(**)().

In Christ,
Steven Watanabe