Practical Template Programming - Learn C++ for Game Development - page 198

The RegisterEvent method first searched the m_eventMap variable using find to see if an Event with
the same eventID already exists. If it does not, then a new Event object is created and added to the
unordered_map . The AttachEvent and DetachEvent methods find the Event object for the specified
eventID and add or detach the supplied EventHandler object, using the code shown in Listing 21-11.
Listing 21-11. The EventManager AttachEvent and DetachEvent Methods
void EventManager::AttachEvent(EventID eventId, EventHandler& eventHandler)
{
EventMapIterator result = m_eventMap.find(eventId);
assert(result != m_eventMap.end());
if (result != m_eventMap.end())
{
assert(result->second);
result->second->AttachListener(eventHandler);
}
}
void EventManager::DetachEvent(EventID eventId, EventHandler& eventHandler)
{
EventMapIterator result = m_eventMap.find(eventId);
assert(result != m_eventMap.end());
if (result != m_eventMap.end())
{
assert(result->second);
result->second->DetachListener(eventHandler);
}
}
These methods are quite simple: They find the Event object for the given eventID and call the Event
class's AttachListener or DetachListener , respectively. The SendEvent and SendEventToHandler
methods are equally simple and shown in Listing 21-12.
Listing 21-12. The EventManager SendEvent and SendEventToHandler Methods
void EventManager::SendEvent(EventID eventId)
{
EventMapIterator result = m_eventMap.find(eventId);
if (result != m_eventMap.end())
{
assert(result->second);
if (result->second)
{
result->second->Send();
}
}
}