Practical Template Programming - Learn C++ for Game Development - page 196

Listing 21-7. The Event::Send Method
void Event::Send()
{
for (auto& listener : m_listeners)
{
if (listener != nullptr)
{
listener->HandleEvent(this);
}
}
}
The Send method is straightforward. It simply loops all over the m_listeners vector and calls the
HandleEvent method on each valid entry.
The SendToHandler method is given in Listing 21-8. It sends the message to a single EventHandler
rather than all of them.
Listing 21-8. The Event::SendToHandler Method
void Event::SendToHandler(EventHandler& eventHandler)
{
auto found = std::find(m_listeners.begin(), m_listeners.end(), &eventHandler);
if (found != m_listeners.end())
{
(*found)->HandleEvent(this);
}
}
This time we use the find STL algorithm to get an iterator to the entry that stores our EventHandler
and then call HandleEvent if it is found.
Now that we have an interface for EventHandlers and a class to represent Events , we can look at
how the EventManager class is implemented.
The EventManager Implementation
Listing 21-9 shows the member variables and methods contained in the EventManager class.
Listing 21-9. The EventManager Members and Methods
class EventManager
: public Singleton<EventManager>
{
friend void SendEvent(EventID eventId);
template <typename T>
friend void SendEventToHandler(EventID eventId, T* eventHandler);
friend bool RegisterEvent(EventID eventId);