类型安全的事件系统实现

Question

我为我的游戏写了一个事件系统。它工作正常，但有一个很大的缺陷 - 它不是类型安全的，因此需要订阅的回调函数手动强制接收基本事件。现在，我正在尝试使用模板实现类型安全版本。我通常对这个话题很满意，但显然不是专家。

首先，这里是一些代码演示如何我想使用的事件：

定义的衍生事件

// Derived Events 
class ClickEvent : public Event 
{ 
public: 
    float x; 
    float y; 
}; 

class RenderNodeCreatedEvent : public Event 
{ 
public: 
    unsigned long long int renderNodeId; 
}; 

创建它们并（在主程序例如用于测试目的）使用它们

// Create the on event functions 
std::function<void(const ClickEvent &)> onClickFunction = [](const ClickEvent & event) 
{ 
    std::cout << std::endl << "Mouse clicked at position: " << event.x << event.y; 
}; 

std::function<void(const RenderNodeCreatedEvent &)> onRenderNodeCreatedFunction = [](const RenderNodeCreatedEvent & event) 
{ 
    std::cout << std::endl << "Render node created with id: " << event.renderNodeId; 
}; 

// Create the events 
ClickEvent clickEvent; 
clickEvent.x = 300.f; 
clickEvent.y = 255.5f; 

RenderNodeCreatedEvent renderNodeCreatedEvent; 
renderNodeCreatedEvent.renderNodeId = 26234628374324; 

// Create the event manager and subscribe the event functions 
EventManager eventManager; 
eventManager.Subscribe(onClickFunction); 
eventManager.Subscribe(onRenderNodeCreatedFunction); 

// Raise the events 
eventManager.Raise(clickEvent); 
eventManager.Raise(renderNodeCreatedEvent); 

这是我试图产生std::size_t类型的唯一ID为每个派生事件类：

class BaseEvent 
{ 
public: 
    typedef std::size_t ID; 

    BaseEvent() = default; 
    virtual ~BaseEvent() = default; 

protected: 
    static ID GetNextID() 
    { 
     static ID id = 0; 
     return id++; 
    } 
}; 

class Event : public BaseEvent 
{ 
public: 
    Event() = default; 
    virtual ~Event() = default; 

    // Sets a unique id for the event the first time this function is called 
    ID GetID() 
    { 
     static ID id = BaseEvent::GetNextID(); 
     return id; 
    } 
}; 

最后，这是我的（可怕的）尝试在事件管理器，可以提供上述功能。我非常努力地管理正确的投射和/或存储不同类型的回调函数。回调包装器不起作用 - 它只是一个基本的想法，我必须解决这个问题，所以我把它包含在帖子中。

class EventManager 
{ 
public: 
    // Define the template callback type 
    template <class DerivedEvent> 
    using TCallback = std::function<void(const DerivedEvent &)>; 

public: 
    EventManager() = default; 
    ~EventManager() = default; 

    template<class DerivedEvent> 
    void Subscribe(TCallback<DerivedEvent> callback) 
    { 
     // Get the index of the callback list this callback will be added to 
     Event::ID id = DerivedEvent::GetID(); 

     // This won't work sinve TCallback is a different type than TCallback<Event> 
     callbackListList[id].push_back(callback); 
    } 

    template <class DerivedEvent> 
    void Raise(DerivedEvent event) 
    { 
     // Get the type of the event and therefore the index in the callbackListList 
     Event::ID = DerivedEvent::GetID(); 

     /// How to cast the events back 
     // Get the respective list of callback functions 
     std::vector<TCallback<DerivedEvent>> /*&*/ callbackList; 

     // Create a callback wrapper of with the type 'derived event' ????? 
     CallbackWrapper<DerivedEvent> callbackWrapper(/*derived callback*/); 
     // Call the callback wrapper using the base event ????? 
    } 

    template <typename DerivedEvent> 
    class CallbackWrapper 
    { 
    public: 
     CallbackWrapper(TCallback<DerivedEvent> callback) : callback(callback) {} 

     void operator() (const Event & event) 
     { 
      callback(static_cast<const Event<DerivedEvent> &>(event).event); 
     } 

    private: 
     TCallback<DerivedEvent> callback; 
    }; 

private: 
    std::vector<std::vector<TCallback<Event>>> callbackListList; 
}; 

我知道这是很多代码，但我觉得这是展示我所谈论的最简单的方法。

感谢您的帮助，阿德里安

编辑： 事件类都必须声明为模板，以获得唯一ID派生类型。现在

template <class DerivedEvent> 
class Event : public BaseEvent 

从事件继承时：

class ClickEvent : public Event<ClickEvent> 
class RenderNodeCreatedEvent : public Event<RenderNodeCreatedEvent> 

最后，eventmanager进行只能存储类型的回调的矢量的矢量BaseEvent

private: 
    std::vector<std::vector<TCallback<BaseEvent>>> callbackListList; 

Answer 1

长一些研究之后，我发现这篇文章基本上解决了ECS事件/信使实现问题：

https://codereview.stackexchange.com/questions/79211/ecs-event-messaging-implementation