Meta tables

How do you make an object with something resembling methods in Lua?

Lua has a very minimal mechanism which involves taking a Table and associating it with what is called a metatable. The same technique can used with User data type.

This metatable has special keys like __index which can be used to define a table of functions with with the Colon Operator syntax can be used like methods. This code sample provides an example of this:

local MT = {}

MT.__index = {}
MT.__index.oneMethod = function(T)      return "OneMethod on "..T.name;     end
MT.__index.anotherMethod = function(T)  return "AnotherMethod on "..T.name; end

function main(Data)
   local O = {}
   O.name = "Fred"
   setmetatable(O, MT)
   O:anotherMethod()
   O:oneMethod()
end

The best way to see it in action is in the Developing in the Translator :