我为我的游戏编写了一个事件系统。它可以正常工作,但有一个很大的缺陷——它不是类型安全的,因此需要订阅回调函数手动将接收到的基础事件进行强制类型转换。现在,我正在尝试使用模板实现类型安全的版本。我对这个主题的理解通常还可以,但显然不是专家。
首先,这里有一些演示如何使用事件的代码:
定义衍生事件
// Derived Events
class ClickEvent : public Event
{
public:
float x;
float y;
};
class RenderNodeCreatedEvent : public Event
{
public:
unsigned long long int renderNodeId;
};
创建它们并使用它们(例如在主程序中进行测试)
// 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);
这是我尝试为每个派生的事件类生成一个std :: size_t
类型的唯一ID:
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,这是我尝试编写的事件管理器(可能很糟糕),可以提供上述功能。我很难正确地转换数据类型或存储不同类型的回调函数。回调函数包装器无效——只是我为解决此问题想到的一个基本思路,因此我将其包含在帖子中。
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,但我觉得这是演示我所说的最简单的方法。
谢谢你的帮助,Adrian。
编辑:事件类必须声明为模板以获取派生类型的唯一ID。
template <class DerivedEvent>
class Event : public BaseEvent
现在,当继承自事件(Event)时:
class ClickEvent : public Event<ClickEvent>
class RenderNodeCreatedEvent : public Event<RenderNodeCreatedEvent>
最后,EventManager只能存储一个类型为BaseEvent回调函数的向量的向量。
private:
std::vector<std::vector<TCallback<BaseEvent>>> callbackListList;
EventManager
可能应该是一种模板,可以管理特定类型的回调。这样,就很容易实现类型安全性。 - Phil1970EventManager
使用EventManagerData<T>
存储数据... 至少如果事件管理器是单例,这将是一种简单的方法。 - Phil1970