tables_oop1.lua

-- remember, doc comments starts with --- (three dashes).

local a = collectgarbage("count") * 1024

--- Docs for SuperClass (this is a Metatable)
local SuperClass = {
	__tostring = function()
		return "SuperClass.__tostring method."
	end,
}

function SuperClass.new()
	--- Docs for SuperClass
	--- @class SuperClass
	local self = {
		--- Docs for inherited_method
		inherited_method = function()
			return "this is an inherited method"
		end,
	}

	return setmetatable(self, SuperClass)
end

-----------------------------------------------------------------------------------------------

--- Docs for Class (this is a Metatable)
local Class = {
	__tostring = function()
		return "Class.__tostring method"
	end,
}

-- "static" method should be defined in the Class table.
function Class.new()
	-- private attrs should be defined here (function local scope)
	local private = "this is a private attr"

	--- Docs for the instance
	--- @class Class : SuperClass
	local self = SuperClass.new()

	--- Docs for public_field
	self.public_field = "this is a public attr"

	--- Docs for get_private
	function self.get_private()
		return private
	end

	-- Here is where the magic happens:
	-- With this line, the class will inherit the SuperClass metamethods
	-- and Class will have the Class meta.
	return setmetatable(self, setmetatable(Class, SuperClass))
end

----------------------------------------- Here a Demo -----------------------------------------

local i = Class.new()

print(Class)

-- This would print `nil`. but it is commented because it also produces an LS warning
-- print(i.private_field)

print(i)
print(i.public_field)
print(i.get_private())
print(i.inherited_method())

local b = collectgarbage("count") * 1024
print("\nBytes before instantiation: " .. a .. " Bytes")
print("Bytes after instantiation:  " .. b .. " Bytes")
print("Estimated Bytes running:    " .. b - a .. " Bytes")
-----------------------------------------------------------------------------------------------

-- Making the Class table local, you need to import it where you want to use it:
--     local Class = require("this_file")
--     local i = Class.new()
-- Alternatively, you can make it global, so you can use it just requiring the file (is not recommended):
--     require("this_file")
--     local i = Class.new()
return Class