How to extend index from hooks?

Lua
5

OOPS! My fault, there’s a typo in the code. :wink:

There isn’t really such a thing as immutable data in Lua

TL;DR

To explain more further… One can always play with table’s metamethods to gain poor man’s sort of “immutability” as some sort of “safety net” (if needed)…

function immutable(tbl)
  return setmetatable({}, {
    __index = tbl,
    __newindex = function(tbl, key, val)
      error('Cannot modify read-only table')
    end,
    __metatable = false
  })
end

local t = immutable { x = 1, y = 2, z = 3 } -- new "immutable" table `t`

It’s a nice trick but MUST NOT be considered as a “security feature” or something like that because the rawset() call can still be used to override this!

So, yes, there is simply no real immutability in Lua. :slight_smile: