How does __newindex actually work in OOP? (WILL PAY)

[topaz chasm]

I'm exploring OOP and noticing many people use __newindex to monitor property changes, but I don't understand its functioning despite reviewing Roblox documentation.
Thank you for helping me, I'll pay you with a heart full of love.

[novel nimbus]

__newindex is essientally just a function that fires when an new index is assigned to

local metatable = {}

metatable.__newindex = function(t, i, v)
    print(`t[{i}] was assigned to. v: {v}`)
end

local t = setmetatable({
    x = 1
}, metatable)

t.x = 2 -- will print, since x is being assigned to.
doSomething(t.y) -- will not print, since it's being accessed. (use __index for that.)

so essientally, if it exists, __newindex will only fire if you're adding something that didn't already exist to the dictionary

[topaz chasm]

How about detect changes of properties ?

[novel nimbus]

what?

that's probably a better way to say it

uhh

[topaz chasm]

i want it fires when i change the index that already exists

Is there any way?

[novel nimbus]

just check if it already exists

[topaz chasm]

like the .Changed event for instance

[novel nimbus]

__newindex = funciton(t, k, v)
    if t[k] then
      -- your code here
    end
end

you can use rawset/rawget to change them without firing the metamethods.