I'm trying to write a macro to make a specific usage of callbacks in C++ easier. All my callbacks are member functions and will take this as first argument and a second one whose type inherits from a common base class.
The usual way to go is:
register_callback(boost::bind(&my_class::member_function, this, _1));
I'd love to write:
register_callback(HANDLER(member_function));
Note that it will always be used within the same class.
Even if typeof is considered as a bad practice, it sounds like a pretty solution to the lack of __class__ macro to get the current class name.
The following code works:
typedef typeof(*this) CLASS;
boost::bind(& CLASS :: member_function, this, _1)(my_argument);
but I can't use this code in a macro which will be given as argument to register_callback.
I've tried:
#define HANDLER(FUN) \
boost::bind(& typeof(*this) :: member_function, this, _1);
which doesn't work for reasons I don't understand. Quoting GCC documentation:
A
typeof-construct can be used anywhere a typedef name could be used.
My compiler is GCC 4.4, and even if I'd prefer something standard, GCC-specific solutions are accepted.
Your problem might be that typeof yields my_class&. It appears to work with boost::remove_reference:
#include <boost/bind.hpp>
#include <boost/type_traits.hpp>
#include <iostream>
struct X
{
void foo(int i) { std::cout << i << '\n'; }
void bar() {boost::bind(&boost::remove_reference<typeof(*this)>::type::foo, this, _1)(10); }
};
int main()
{
X x;
x.bar();
}
It might be more portable to use BOOST_TYPEOF, and in C++0x decltype