Lua :new from C API - c

Question

I am working on a scripting layer for my game engine. Currently I am using a Script as a Class, adding a method to the "Table" named new. This function basically created an instantiated copy of the Class. I call this function from the C API when an instance of the script is needed.
function PlayerController:new(o)
print('A new instance of the PlayerController has been created');
o = o or {}
setmetatable(o, self)
self.__index = self
return o
end
My question is: How can I take the above Lua code, and move that into C so it is not required to be added to every script file I write for this system?

Answer 1

You might want to create a class declaration function to do this for you. Here is a complete "helper.lua" file:
local lib = {type = 'helper'}
local CALL_TO_NEW = {__call = function(lib, ...) return lib.new(...) end}
function lib.class(class_name, tbl)
local lib = tbl or {}
lib.type = class_name
lib.__index = lib
-- Default "new" method
function lib.new()
return setmetatable({}, lib)
end
-- Enable foo.Bar() instead of foo.Bar.new()
return setmetatable(lib, CALL_TO_NEW)
end
return lib
Usage example:
local helper = require 'helper'
local lib = helper.class 'foo.Bar'
-- optional new function if there needs to be some argument handling
function lib.new(args)
local self = {}
-- ...
return setmetatable(self, lib)
end
return lib
lub.class
This is a real world minimal class declaration and setup system. It is used in many luarocks such as xml, yaml, dub, etc:
documentation
source code