No class template named 'apply' with regard to Boost Signals2 - c++

Question

I have followed the Boost tutorial, "Passing Slots (Intermediate)", at reference [ 1 ] to the letter yet I am getting a weird error with my code that I cannot decipher or find any help with regard to. My code is below:
[ 1 ] - http://www.boost.org/doc/libs/1_55_0/doc/html/signals2/tutorial.html#idp204830936
namespace GekkoFyre {
class TuiHangouts {
private:
typedef boost::signals2::signal<void()> onRosterUpdate;
typedef onRosterUpdate::slot_type onRosterUpdateSlotType;
void logMsgs(std::string message, const xmppMsgType &msgType);
void logMsgsDrawHistory();
// Slots
boost::signals2::connection doOnRosterUpdate(const onRosterUpdateSlotType &slot);
onRosterUpdate rosterUpdate;
};
}
boost::signals2::connection GekkoFyre::TuiHangouts::doOnRosterUpdate(
const GekkoFyre::TuiHangouts::onRosterUpdateSlotType &slot)
{
return rosterUpdate.connect(slot);
}
The problem is with this specifically:
void GekkoFyre::TuiHangouts::logMsgs(std::string message, const xmppMsgType &msgType)
{
doOnRosterUpdate(&GekkoFyre::TuiHangouts::logMsgsDrawHistory);
}
I get the error:
In file included from /usr/include/boost/function/detail/maybe_include.hpp:13:0,
from /usr/include/boost/function/detail/function_iterate.hpp:14,
from /usr/include/boost/preprocessor/iteration/detail/iter/forward1.hpp:47,
from /usr/include/boost/function.hpp:64,
from /usr/include/boost/signals2/signal.hpp:18,
from /usr/include/boost/signals2.hpp:19,
from /home/phobos/Programming/gecho/src/tui/chat.hpp:47,
from /home/phobos/Programming/gecho/src/tui/chat.cpp:35:
/usr/include/boost/function/function_template.hpp: In instantiation of 'void boost::function0<R>::assign_to(Functor) [with Functor = void (GekkoFyre::TuiHangouts::*)(); R = void]':
/usr/include/boost/function/function_template.hpp:722:7: required from 'boost::function0<R>::function0(Functor, typename boost::enable_if_c<(boost::type_traits::ice_not<(boost::is_integral<Functor>::value)>::value), int>::type) [with Functor = void (GekkoFyre::TuiHangouts::*)(); R = void; typename boost::enable_if_c<(boost::type_traits::ice_not<(boost::is_integral<Functor>::value)>::value), int>::type = int]'
/usr/include/boost/function/function_template.hpp:1071:16: required from 'boost::function<R()>::function(Functor, typename boost::enable_if_c<(boost::type_traits::ice_not<(boost::is_integral<Functor>::value)>::value), int>::type) [with Functor = void (GekkoFyre::TuiHangouts::*)(); R = void; typename boost::enable_if_c<(boost::type_traits::ice_not<(boost::is_integral<Functor>::value)>::value), int>::type = int]'
/usr/include/boost/function/function_template.hpp:1126:5: required from 'typename boost::enable_if_c<(boost::type_traits::ice_not<(boost::is_integral<Functor>::value)>::value), boost::function<R()>&>::type boost::function<R()>::operator=(Functor) [with Functor = void (GekkoFyre::TuiHangouts::*)(); R = void; typename boost::enable_if_c<(boost::type_traits::ice_not<(boost::is_integral<Functor>::value)>::value), boost::function<R()>&>::type = boost::function<void()>&]'
/usr/include/boost/signals2/detail/slot_template.hpp:160:24: required from 'void boost::signals2::slot<R(Args ...), SlotFunction>::init_slot_function(const F&) [with F = void (GekkoFyre::TuiHangouts::*)(); SlotFunction = boost::function<void()>; R = void; Args = {}]'
/usr/include/boost/signals2/detail/slot_template.hpp:85:27: required from 'boost::signals2::slot<R(Args ...), SlotFunction>::slot(const F&) [with F = void (GekkoFyre::TuiHangouts::*)(); SlotFunction = boost::function<void()>; R = void; Args = {}]'
/home/phobos/Programming/gecho/src/tui/chat.cpp:802:74: required from here
/usr/include/boost/function/function_template.hpp:924:9: error: no class template named 'apply' in 'struct boost::detail::function::get_invoker0<boost::detail::function::member_ptr_tag>'
handler_type;
If anyone could assist with this then it would be immensely appreciated. As I said previously, I did some research and couldn't really find much of anything. It seems kind of unique to me, perhaps, and I did follow the tutorial to the letter. I know this isn't always the right thing to do but from what I can gather through research, this code should work.

Answer 1

&GekkoFyre::TuiHangouts::logMsgsDrawHistory is a member function pointer, which has the type void (GekkoFyre::TuiHangouts::*)(). This isn't like any other function, and so it cannot be called like any other function. Signals2 will attempt to call this with the syntax func(), but there is no this pointer here. To provide it with a this pointer, you would use the syntax (p->*func)(). The p here becomes the this pointer. boost::bind (also in the C++ standard since 2011 called std::bind) will wrap this up as a function object that can be called as func() by calling (p->*func)().