Re: [boost] [bind] Automatic argument counting

From: Robert Dailey (rcdailey_at_[hidden])
Date: 2008-03-13 15:11:19

On Thu, Mar 13, 2008 at 1:32 PM, Robert Dailey <rcdailey_at_[hidden]> wrote:

> On Thu, Mar 13, 2008 at 1:03 PM, vicente.botet <vicente.botet_at_[hidden]>
> wrote:
> >
> > >
> > >
> > > This will not work because of this line in bind_mem_fn.hpp:
> > >
> > > #include <boost/function_types/function_arity.hpp>
> > >
> > > function_types is not in 1.34.1 :(
> >
> >
> > Why you don't take also this file is this could help you ;-)? You can
> > get it
> > from the trunk.
>
>
> Because, like with all other boost library components, I'm afraid of
> cherry picking files because they are usually involved in a large web of
> dependencies. More than likely I won't be just taking one file, I'll be
> taking many files and doing a lot of manual hunting. Even if I get all the
> files, there might also be compatibility issues when taking Boost 1.35files and placing them in boost
> 1.34.1. I would rather not have to wait for subtle issues to arrive.
>

I was actually able to get this working, surprisingly enough. I copied over
function_types into boost 1.34.1 and at the very least bind_mem_fn seems to
work.

However, I'm having a bit of an issue with my design that uses bind_mem_fn.
Right now I have a class that has a boost::tuple of objects which, on
construction, bind a function to a boost::signal. In my constructor, I fill
the tuple with various references to member functions of the class
initializing the tuple. For example:

using boost::dataflow::utility::bind_mem_fn;

Rocket_Input::Rocket_Input()
    : m_subscriptions(  bind_mem_fn( &Rocket_Input::HandleKey, this ),
                        bind_mem_fn( &Rocket_Input::HandleMouseMotion, this
),
                        bind_mem_fn( &Rocket_Input::HandleMouseWheel, this
),
                        bind_mem_fn( &Rocket_Input::HandleMouseButton, this
)
                        )
{}

While this does compile, it will crash any time that one of the function
objects is called because in the initializer list, 'this' references a NULL
pointer when the class object was allocated on the heap via a call to 'new'.
Is there a way I can initialize my tuple so that 'this' will be a valid
pointer? For now, I might just go ahead and make my m_subscriptions tuple a
boost::scoped_ptr and initialize it in the constructor body and see if that
helps.

Thanks.