Difference between middleclass, classic and oo

[winterwolf]

-- https://github.com/kikito/middleclass
local middleclass = require "middleclass"
local CreatureMC = middleclass("CreatureMC")
function CreatureMC:__call() print("CreatureMC was called!") end
local AnimalMC = CreatureMC:subclass("AnimalMC")
local CatMC = AnimalMC:subclass("CatMC")
local tomMC = CatMC()
print(tomMC) -- instance of class CatMC
print(pcall(tomMC)) -- called, no errors


-- https://github.com/rxi/classic
local classic = require "classic"
local CreatureCL = classic:extend()
function CreatureCL:__call() print("CreatureCL was called!") end
local AnimalCL = CreatureCL:extend()
local CatCL = AnimalCL:extend()
local tomCL = CatCL()
print(tomCL) -- nil !?
print(pcall(tomCL)) -- called, error (attempt to call a nil value)


-- https://github.com/limadm/lua-oo
local oo = require "oo"
local CreatureOO = oo()
function CreatureOO:__call() print("CreatureOO was called!") end
local AnimalOO = CreatureOO:extend()
local CatOO = AnimalOO:extend()
local tomOO = CatOO()
print(tomOO) -- table
print(pcall(tomOO)) -- error (attempt to call a table value)

[winterwolf]

return self after call solved the issue.

[winterwolf]

... No, wait. In this case CreatureCL called twice 🤦‍♂️

[winterwolf]

We can add return setmetatable({}, self) into Object:new() and call it manually to create instances. This solution seems would work well BUT it will not solve the same problem #13 with __index and __newindex.