Initial commit

sys/apis/class.lua

@@ -0,0 +1,46 @@
+-- From http://lua-users.org/wiki/SimpleLuaClasses
+-- (with some modifications)
+
+-- class.lua
+-- Compatible with Lua 5.1 (not 5.0).
+return function(base)
+  local c = { }    -- a new class instance
+  if type(base) == 'table' then
+    -- our new class is a shallow copy of the base class!
+    for i,v in pairs(base) do
+      c[i] = v
+    end
+    c._base = base
+  end
+  -- the class will be the metatable for all its objects,
+  -- and they will look up their methods in it.
+  c.__index = c
+
+  -- expose a constructor which can be called by <classname>(<args>)
+  setmetatable(c, {
+    __call = function(class_tbl, ...)
+      local obj = {}
+      setmetatable(obj,c)
+      if class_tbl.init then
+        class_tbl.init(obj, ...)
+      else
+        -- make sure that any stuff from the base class is initialized!
+        if base and base.init then
+          base.init(obj, ...)
+        end
+      end
+      return obj
+    end
+  })
+
+  c.is_a =
+    function(self, klass)
+      local m = getmetatable(self)
+      while m do 
+        if m == klass then return true end
+        m = m._base
+      end
+      return false
+    end
+  return c
+end