c++ - 如何将成员函数作为参数传递？

Question

我有以下类(class):

typedef void (*ScriptFunction)(void);
typedef std::unordered_map<std::string, std::vector<ScriptFunction>> Script_map;

class EventManager
{
public:

    Script_map subscriptions;

    void subscribe(std::string event_type, ScriptFunction handler);
    void publish(std::string event);

};

class DataStorage
{
    std::vector<std::string> data;
public:

    EventManager &em;

    DataStorage(EventManager& em);
    void load(std::string);
    void produce_words();


};
DataStorage::DataStorage(EventManager& em) : em(em) {
    this->em.subscribe("load", this->load);     
};

我希望能够将 DataStorage::load 传递给 EventManager::subscribe，以便稍后调用它。我如何在 C++ 中实现这一点？

Answer 1

最好的方法是使用 std::function :

#include <functional>

typedef std::function<void(std::string)> myFunction;
// Actually, you could and technically probably should use "using" here, but just to follow
// your formatting here

然后，要接受一个函数，您只需要像以前一样做同样的事情:

void subscribe(std::string event_type, myFunction handler);
// btw: could just as easily be called ScriptFunction I suppose

现在是棘手的部分；要传递一个成员函数，你实际上需要 bind DataStorage 的实例到成员函数。这看起来像这样:

DataStorage myDataStorage;
EventManager manager;

manager.subscribe("some event type", std::bind(&DataStorage::load, &myDataStorage));

或者，如果您在 DataStorage 的成员函数内:

manager.subscribe("some event type", std::bind(&DataStorage::load, this));