麻烦与升压信号

Question

我在升压和C++这样的情况：

// Somewhere: 
typedef boost::signals2::signal<void (int KeyCode)> SigKeyPressed; 
typedef SigKeyPressed::slot_type SigKeyPressedType; 

class InputSystem 
{ 
    private: 
     static SigKeyPressed mSigKeyPressed; 
    public: 
     static boost::signals2::connection keyPressed(const SigKeyPressedType &slot); 
}; 

boost::signals2::connection InputSystem::keyPressed(const SigKeyPressedType& slot) 
{ 
    // I tried: 
    return mSigKeyPressed.connect(boost::bind(&slot, this, _1); 
    // Or this: 
    return mSigKeyPressed.connect(slot); 
} 

class GameApplication 
{ 
    public: 
     GameApplication() { InputSystem::keyPressed(&GameApplication::onKeyPressed); } 
     void onKeyPressed(int KeyCode) { /* do something */ } 
}; 

此代码抛出错误的文件与GameApplication：

/usr/include/boost/function/function_template.hpp: In static member function ‘static void boost::detail::function::function_void_mem_invoker1<MemberPtr, R, T0>::invoke(boost::detail::function::function_buffer&, T0) [with MemberPtr = void (GameApplication::*)(sf::Event::KeyEvent&), R = void, T0 = sf::Event::KeyEvent&]’: 
In file included from /usr/include/boost/function/detail/maybe_include.hpp:18:0, 
/usr/include/boost/function/function_template.hpp:913:60: instantiated from ‘void boost::function1<R, T1>::assign_to(Functor) [with Functor = void (GameApplication::*)(sf::Event::KeyEvent&), R = void, T0 = sf::Event::KeyEvent&]’ 
/usr/include/boost/function/function_template.hpp:722:7: instantiated from ‘boost::function1<R, T1>::function1(Functor, typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<InputIterator>::value>::value, int>::type) [with Functor = void (GameApplication::*)(sf::Event::KeyEvent&), R = void, T0 = sf::Event::KeyEvent&, typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<InputIterator>::value>::value, int>::type = int]’ 
/usr/include/boost/function/function_template.hpp:1064:16: instantiated from ‘boost::function<R(T0)>::function(Functor, typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<InputIterator>::value>::value, int>::type) [with Functor = void (GameApplication::*)(sf::Event::KeyEvent&), R = void, T0 = sf::Event::KeyEvent&, typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<InputIterator>::value>::value, int>::type = int]’ 
/usr/include/boost/function/function_template.hpp:1105:5: instantiated from ‘typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<InputIterator>::value>::value, boost::function<R(T0)>&>::type boost::function<R(T0)>::operator=(Functor) [with Functor = void (GameApplication::*)(sf::Event::KeyEvent&), R = void, T0 = sf::Event::KeyEvent&, typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<InputIterator>::value>::value, boost::function<R(T0)>&>::type = boost::function<void(sf::Event::KeyEvent&)>&]’ 
/usr/include/boost/signals2/detail/slot_template.hpp:137:9: instantiated from ‘void boost::signals2::slot1<R, T1, SlotFunction>::init_slot_function(const F&) [with F = void (GameApplication::*)(sf::Event::KeyEvent&), R = void, T1 = sf::Event::KeyEvent&, SlotFunction = boost::function<void(sf::Event::KeyEvent&)>]’ 
/usr/include/boost/signals2/detail/slot_template.hpp:81:9: instantiated from ‘boost::signals2::slot1<R, T1, SlotFunction>::slot1(const F&) [with F = void (GameApplication::*)(sf::Event::KeyEvent&), R = void, T1 = sf::Event::KeyEvent&, SlotFunction = boost::function<void(sf::Event::KeyEvent&)>]’ 
src/Core/GameApplication.cpp:14:82: instantiated from here 
/usr/include/boost/function/function_template.hpp:225:11: error: no match for call to ‘(boost::_mfi::mf1<void, GameApplication, sf::Event::KeyEvent&>) (sf::Event::KeyEvent&)’ 
/usr/include/boost/bind/mem_fn_template.hpp:160:7: note: candidates are: R boost::_mfi::mf1<R, T, A1>::operator()(T*, A1) const [with R = void, T = GameApplication, A1 = sf::Event::KeyEvent&] 
/usr/include/boost/bind/mem_fn_template.hpp:179:7: note:     R boost::_mfi::mf1<R, T, A1>::operator()(T&, A1) const [with R = void, T = GameApplication, A1 = sf::Event::KeyEvent&] 

Answer 1

InputSystem::keyPressed期望的槽（一个可调用对象），但GameApplication的ctor只传递一个指向成员的指针。尝试是这样的：

GameApplication() 
    { 
    InputSystem::keyPressed(bind(&GameApplication::onKeyPressed, this, _1)); 
    } 

编辑：这对我的作品（编译并打印“键按下与110”）：

#include <boost/signals2.hpp> 
#include <boost/bind.hpp> 
#include <iostream> 

typedef boost::signals2::signal<void (int KeyCode)> SigKeyPressed; 
typedef SigKeyPressed::slot_type SigKeyPressedType; 

class InputSystem 
{ 
    private: 
     static SigKeyPressed mSigKeyPressed; 
    public: 
     static boost::signals2::connection keyPressed(const SigKeyPressedType &slot); 
     static void DoSignal(int KeyCode) {mSigKeyPressed(KeyCode);} 
}; 

boost::signals2::connection InputSystem::keyPressed(const SigKeyPressedType& slot) 
{ 
    return mSigKeyPressed.connect(slot); 
} 

SigKeyPressed InputSystem::mSigKeyPressed; 

class GameApplication 
{ 
    public: 
     GameApplication() { InputSystem::keyPressed(boost::bind(&GameApplication::onKeyPressed, this, _1)); } 
     void onKeyPressed(int KeyCode) { std::cout << "key pressed with " << KeyCode << std::endl; } 
}; 

int main() 
{ 
    GameApplication g;  
    InputSystem::DoSignal(110); 
}