lua/lib/class.lua

   1 -- class.lua
   2 -- Compatible with Lua 5.1 (not 5.0).
   3 function class(base,ctor)
   4   local c = {}     -- a new class instance
   5   if not ctor and type(base) == 'function' then
   6       ctor = base
   7       base = nil
   8   elseif type(base) == 'table' then
   9    -- our new class is a shallow copy of the base class!
  10       for i,v in pairs(base) do
  11           c[i] = v
  12       end
  13       c._base = base
  14   end
  15   -- the class will be the metatable for all its objects,
  16   -- and they will look up their methods in it.
  17   c.__index = c
  18
  19   -- expose a ctor which can be called by <classname>(<args>)
  20   local mt = {}
  21   mt.__call = function(class_tbl,...)
  22     local obj = {}
  23     setmetatable(obj,c)
  24     if ctor then
  25        ctor(obj,...)
  26     else
  27     -- make sure that any stuff from the base class is initialized!
  28        if base and base.init then
  29          base.init(obj,...)
  30        end
  31     end
  32     return obj
  33   end
  34   c.init = ctor
  35   c.is_a = function(self,klass)
  36       local m = getmetatable(self)
  37       while m do
  38          if m == klass then return true end
  39          m = m._base
  40       end
  41       return false
  42     end
  43   setmetatable(c,mt)
  44   return c
  45 end
  46