Generic/event.lua

   1 -- Functions we use here.
   2 local create = QuestHelper.create
   3 local createCallback = QuestHelper.createCallback
   4 local reference = QuestHelper.reference
   5 local release = QuestHelper.release
   6
   7 -- The metatable for Event objects.
   8 local Event = {}
   9
  10 function Event:onCreate()
  11   rawset(self, "set", create())
  12 end
  13
  14 function Event:onRelease()
  15   local set = rawget(self, "set")
  16   for cb in pairs(set) do release(cb) end
  17   release(set)
  18 end
  19
  20 -- Adds a reference to callback to if it hasn't already been added.
  21 -- If callback is a function, creates a callback.
  22 -- You could probably register another event here as if it were a callback, but I doubt that would be a great idea.
  23 -- Returns the passed (or created) callback.
  24 function Event:register(callback, ...)
  25   local set = rawget(self, "set")
  26   if type(callback) == "function" then
  27     callback = createCallback(callback, ...)
  28     set[callback] = true
  29   else
  30     if not set[callback] then
  31       set[reference(callback)] = true
  32     end
  33   end
  34
  35   return callback
  36 end
  37
  38 -- Unregisters a callback previously passed to or returned from register.
  39 function Event:unregister(callback)
  40   local set = rawget(self, "set")
  41   assert(set[callback], "Wasn't previously registered.")
  42   set[callback] = nil
  43   release(callback)
  44 end
  45
  46 -- Invokes all associated callbacks with passed arguments.
  47 function Event:invoke(...)
  48   local set = rawget(self, "set")
  49   for cb in pairs(set) do cb(...) end
  50 end
  51
  52 -- Allows event to be invoked as if it were a function.
  53 Event.__call = Event.invoke
  54
  55 Event.__newindex = function()
  56   assert(false, "Shouldn't assign values.")
  57 end
  58
  59 Event.__index = function(_, key)
  60   return rawget(Event, key)
  61 end
  62
  63 local function createEvent()
  64   return create(Event)
  65 end
  66
  67 QuestHelper.createEvent = createEvent