c++ - 如何将函数指针传递给绑定(bind)？

Question

我有以下代码:

_createNewObjectlistener = eventDispatcher->addCustomEventListener(Constants::EVENT_CREATE_OBJECT, std::bind(&ObjectPlacementManager::receiveCreateObjectEvent, this, std::placeholders::_1));
_eventListeners.insert(_createNewObjectlistener);

_moveNewObjectlistener = eventDispatcher->addCustomEventListener(Constants::EVENT_MOVE_NEW_OBJECT, std::bind(&ObjectPlacementManager::receiveMoveCurrentGameObjectEvent, this, std::placeholders::_1));
_eventListeners.insert(_moveNewObjectlistener);

.... many more listeners created

由于每个监听器的创建代码之间的唯一区别是 Constant::EVENT_NAME和被调用的函数，我试图将它封装到一个函数中。

bind 的结果必须是 const std::function<void(EventCustom*)>& 类型

类似ObjectPlacementManager::receiveMoveCurrentGameObjectEvent的函数都有相同的签名:

void receiveMoveCurrentGameObjectEvent(EventCustom* event){
 ....
}

我试过:How to pass argument to std::bind to a function?

typedef void (*callback_function)(EventCustom*);

EventListenerCustom* createCustomListener(callback_function func, std::string EVENT){
    auto eventDispatcher = _dragNode->getEventDispatcher();
    auto listener = eventDispatcher->addCustomEventListener(EVENT, std::bind(&func, this, std::placeholders::_1));
    _eventListeners.insert(_createNewObjectlistener);
    return listener;
}

但我得到的错误是:

No viable conversion from '__bind<void (**)(cocos2d::EventCustom *), bejoi::ObjectPlacementManager *, const std::__1::placeholders::__ph<1> &>' to 'const std::function<void (EventCustom *)>'

我也试过做一个函数:

EventListenerCustom* createCustomListener(void* func, std::string EVENT){
    auto eventDispatcher = _dragNode->getEventDispatcher();
    auto listener = eventDispatcher->addCustomEventListener(EVENT, std::bind(func, this, std::placeholders::_1));
    return listener;
}

但我得到的错误是:

No viable conversion from '__bind<void *&, mynamespace:: ObjectPlacementManager *, const std::__1::placeholders::__ph<1> &>' to 'const std::function<void (EventCustom *)>'

Answer 1

第一个错误是因为您获取了函数指针的地址。因此，您将一个指向函数指针的指针传递给 std::bind。

第二个错误是因为您使用了 void * 并以某种方式期望它起作用!

试试这个 MCVE:

struct Event {};

struct Dispatcher {
  void addListener(int, const std::function<void(Event *)> &) {}
};

struct Manager {
  void receive(Event *) {}

  void addListener(int type, void (Manager::*receiver)(Event *)) {
    dis.addListener(type, std::bind(receiver, this, std::placeholders::_1));
  }

  void test() {
    addListener(42, &Manager::receive);
  }

  Dispatcher dis;
};