将成员函数和 lambda 传递给 std::function

Question

我正在尝试创建 control/window 类似于在 C# Windows Forms/WPF 中完成的事件。每个事件 class 都包含一个参数类型并传递该类型以及指向发送对象的指针。当使用 lambda 函数时，这一切都很好，但当我尝试向事件添加成员函数时，我得到了 C2276 '&': illegal operation on bound member function expression 和 C2660 'Event<MouseButtonEventArgs>::add': function does not take 1 arguments.

的编译错误

我如何创建一个可以从任何 class 获取 lambda 函数和成员函数的事件 class（无论 class 是否是 "sender"）？

Event.h

template<class Args> struct EventListener {

    /* The function type to be called by the event. */
    typedef function<void(ControlBaseSPtr, Args&)> ArgsFunction;
    string name;
    ArgsFunction function;
};

template<class Args> class Event {

    /* The function type to be called by the event. */
    typedef function<void(ControlBaseSPtr, Args&)> ArgsFunction;
    deque<EventListener<Args>> listeners;

    Event(EventDirections direction) {
        this->direction = direction;
    }

    void add(const string& name, ArgsFunction function) {
        EventListener<Args> listener = EventListener<Args>(name, function);
        for (auto it = listeners.begin(); it != listeners.end(); it++) {
            if (it->name == name) {
                throw exception("Event::operator+= listener already exists in the event");
            }
        }
        listeners.push_back(listener);
    }

    //...
};

Control.h

class ControlBase {
    Event<MouseEventArgs> _eventMouseMovedGlobal;
    Event<MouseButtonEventArgs> _eventMouseButtonGlobal;

    ControlBase();

    void onMouseMovedGlobal(ControlBaseSPtr sender, MouseEventArgs e);
};

Control.cpp

ControlBase::ControlBase() {
    // Works
    _eventMouseButtonGlobal.add("some name", [](ControlSPtr control, MouseButtonEventArgs e){
        //...
    };

    // Doesn't work
    _eventMouseMovedGlobal.add("some name", bind(&onMouseMovedGlobal, this, placeholders::_2))
    // Doesn't work
    _eventMouseMovedGlobal.add("some name", bind(&onMouseMovedGlobal, this))
}

void ControlBase::onMouseWheelGlobal(ControlBaseSPtr sender, MouseWheelEventArgs e) {
    //...
}

Answer 1

好吧，由于 onMouseMovedGlobal 有 2 个输入参数，因此在创建活页夹时您需要为它们提供占位符或值。所以，而不是

_eventMouseMovedGlobal.add("some name", bind(&onMouseMovedGlobal, this, placeholders::_2))

你需要

_eventMouseMovedGlobal.add("some name", bind(&ControlBase::onMouseMovedGlobal, this, placeholders::_1, placeholders::_2))

将成员函数和 lambda 传递给 std::function

Passing both member functions and lambdas to std::function

c++

events

function

std-function