Question

I’ve been lurking here, trying to figure out if a Functor can do what I need it to do.

What I would like to do is wrap a call to a class method and somehow capture the value that the function returns. Given my Functor class, what will I need to do to turn my comments into code:

template < typename Func >
class MySpecializedFunctor
{
    Func t;
    MyObject& p;
public:

    MyFunctor( MyObject &obj, Func f )
    {
        p = obj;
        t = f;
    }

    void runFunc( ... )
    {
        // Can I use an ellipsis '...' to pass values into t->xxxx() ???

        // Assume the first param is always time, the others are never the same
        bool b = p->t( time( NULL ), /* first value of ... */, /* second value of ... */ );
        if ( !b )
        {
            // log error here
        }
    }
}

Because this is a Functor of sorts, the function being wrapped could have n number of parameters.

Is this possible?

EDIT: I cannot use C++0X.

Answer 1

Use variadic templates:

template <typename... Args>
void runFunc(Args&&... args)
{
  bool b = p->t(time(NULL), std::forward<Args>(args)...);
  if ( !b )
  {
    // log error here
  }
}

Or overload runFunc, if your compiler has no support for variadic templates or perfect forwarding:

// this one support 3 const arguments, you will need to overload
// all variations of arguments count and constness
template <typename Arg1, typename Arg2, typename Arg3>
void runFunc(const Arg1& arg1, const Arg2& arg2, const Arg3& arg3)
{
  bool b = p->t(time(NULL), arg1, arg2, arg3);
  if ( !b )
  {
    // log error here
  }
}