lua: check subject of a method -

obj = {}  function obj:setname(name)     print("obj: ", self)     print("name: ", obj) end 

i create object , assign method above. call way:

obj:setname("blabla") 

the self identifier refers obj. problem function potentially accessed via

obj.setname("blabla") 

in case, obj won't passed argument , "blabla" take place of self parameter instead of serving name. because : operator in function declaration shorthand/sugar syntax for

function obj.setname(self, name) 

can somehow check if self subject/if function has been run colon? cannot told argcount nor can write obj in function directly because instantiated , function refered outside scope define it. idea check if self possesses member "setname"

function obj:setname(name)     if ((type(self) ~= "table") or (self.setname == nil))         print("no subject passed")          return     end      print("obj: ", self)     print("name: ", obj) end 

but that's not clean either.

edit: doing now:

local function checkmethodcaller()     local caller = debug.getinfo(2)      local selfvar, self = debug.getlocal(2, 1)      assert(self[caller.name] == caller.func, [[try call function ]]..caller.name..[[ invalid subject, check correct operator (use : instead of .)]]) end  function obj:setname(name)     checkmethodcaller()      print(self, name) end 

you can assign metatable object , inside setname method check whether self's metatable appropriate:

obj = {} local objmt = {}  setmetatable(obj, objmt)  function obj:setname(name)     if getmetatable(self) ~= objmt         error("panic, wrong self!")  -- or handle more gracefully if wish     end     self.name = name end 

edit:

of course, if intentionally replaces or removes metatable, entirely break function.