Generic/callback.lua

   1 local create = QuestHelper.create
   2 local release = QuestHelper.release
   3 local erase = table.remove
   4 local append = QuestHelper.append
   5
   6 -- The metatable for Callback objects.
   7 local Callback = {}
   8
   9 -- Initiates a callback that will invoke func with some arguments, plus any additional arguments
  10 -- passed at the time the callback is invoked.
  11 function Callback:onCreate(func, ...)
  12   rawset(self, 0, func)
  13   rawset(self, "r", 0)
  14   append(self, ...)
  15 end
  16
  17 function Callback:onRelease()
  18   for i = -1, rawget(self, "r"), -1 do release(rawget(self, i)) end
  19 end
  20
  21 local function cb_release(cb, tbl, ...)
  22   if tbl then
  23     assert(type(tbl) == "table", "Can only release tables.")
  24     local r = rawget(cb, "r")
  25     r = r - 1
  26     rawset(cb, r, tbl)
  27     rawset(cb, "r", r)
  28     cb_release(cb, ...)
  29   end
  30 end
  31
  32 -- The callback doesn't do any special book keeping with the function's arguments.
  33 -- If you would like any of them to be released when the callback is, pass them
  34 -- to this function.
  35 Callback.release = cb_release
  36
  37 local temp = {}
  38
  39 -- Invokes the callback, appending any passed arguments to those assigned when the callback was created.
  40 function Callback:invoke(...)
  41   while erase(temp) do end
  42   append(temp, unpack(self))
  43   append(temp, ...)
  44   return rawget(self, 0)(unpack(temp))
  45 end
  46
  47 -- Allows you to use a callback as if it were a function.
  48 Callback.__call = Callback.invoke
  49
  50 Callback.__newindex = function()
  51   assert(false, "Shouldn't assign values.")
  52 end
  53
  54 Callback.__index = function(_, key)
  55   return rawget(Callback, key)
  56 end
  57
  58 local function createCallback(...)
  59   return create(Callback, ...)
  60 end
  61
  62 QuestHelper.createCallback = createCallback