Re: [boost] singleton raw pointer access

From: Rob Stewart (stewart_at_[hidden])
Date: 2005-04-29 11:59:23

From: Jason Hise <chaos_at_[hidden]>
> Rob Stewart wrote:
> 
> >>>  A & object(proxy);
> >>>
> >>This is clever and would probably work.  However, I have two questions:
> >>
> >>A) What benefits would a 'smart reference' provide that the smart 
> >>pointer doesn't already?
> >
> >Safe access to the controlled object that you don't get with
> >get_unsafe_ptr().
> >
> But that's what the smart pointer itself already provides.  In what 
> circumstances would it be better for client code to work with a smart 
> reference than with a smart pointer?  The smart pointer provides access 

The very one you started this thread with!  You asked whether
get_unsafe_ptr() should be spelled operator *().

You wanted to provide access to the raw pointer/reference in
order to allow for polymorphic usage.  The proxy to which I've
been referring provides a safe means for that because the client
can grab and hold a smart reference which can converts
(explicitly or implicitly, your choice) to T & and T *.

> to singleton members via the -> operator.  A smart reference would be 
> unable to provide access to singleton members via the dot operator 
> without first being cast, assigned, or copied into a reference.
> 
> Why would client code prefer this:
> void Foo (  )
> {
>     MySingleton::reference r = *( MySingleton::pointer (  ) );
>     static_cast < MySingleton & > ( r ).DoSomething (  );
> }
> 
> to this?
> 
> void Foo (  )
> {
>     MySingleton::pointer p;
>     p->DoSomething (  );
> }

That wasn't the purpose and of course you wouldn't choose the
former.

> It seems to me that smart references would be too clumsy to work with, 
> and this would encourage client code to store and use real references 
> just to avoid all the casting.

Are we back on track?

-- 
Rob Stewart                           stewart_at_[hidden]
Software Engineer                     http://www.sig.com
Susquehanna International Group, LLP  using std::disclaimer;