setmetatable issue

[stuck perch]

does setmetatable() work in local scripts? i cant understand, why this doesnt work

local a = setmetatable({}, {val=5})
print(a.val)```

(gives nil when i expect 5)

i also tried using module script, but that also doesnt help
```lua
local test2 = {}
test2.__index = test2

function test2.new()
    return setmetatable({}, {val=5})
end

return test2



local t2 = require(script.Parent.test2)

local obj = t2.new()
print(obj.val)

how to fix it?

[dusk zephyr]

yh they do, they do like in any script there's no reason to it to not work

you just got really confused

even me got a little confused reading that

an easy example would be:

[stuck perch]

i understand them as interfaces from java

maybe im wrong...

[dusk zephyr]

local t = {};
local mt = {};
mt.__index = {val = 5;};

setmetatable(t, mt);

print(t.val);

this would print 5

tell me if any doubts

[stuck perch]

why u set __index before setmetatable?

[dusk zephyr]

because the metatable is what contains the metamethods

and the __index metamethod is one of them

https://gist.github.com/oatmealine/655c9e64599d0f0dd47687c1186de99f

you can read this tho

specifically this

[stuck perch]

thnks

so its smth like operator overriding for table mt
and then u pass methods from mt to t with setmetatable()?

[dusk zephyr]

basically yep

[stuck perch]

alr, how linking in lua works? like setmetatable() copies everything from mt or basically links t to mt? taking into account that u type __index before setmetatable() the 1st variant should be correct

[frigid coyote]

** You are now Level 3! **

[dusk zephyr]

basically take the steps of indexing like this:

1 - it will look up for key first in t
2? - if it does not exist in t it will look if the table owns a metatable
3 - if it does, it will check up if __index metamethod is there
4 - (in this case, we'll think out of __index being a table) if the metamethod is there, it will try to look up for key in the metatable, so no, it does not copy and it is good to imitate OOP

[edgy cloud]

You need to do

setmetatable({}, {__index = {val = 5}})

That's all

[stuck perch]

fr just links, i tested

local mt = {val = 5}

local a = setmetatable({}, mt)
mt.__index = mt
print(a.val)```
and it also works

[dusk zephyr]

yeah cuz setmetatable returns the table you pass

[stuck perch]

as i understood, lua links everything possible f.e.

local function test(tbl)
    tbl[1]=1
end

local a = {2}
test(a)
print(a[1])```
out = 1

is it built in way to manually copy the whole table so local one doesnt effect global?

[dusk zephyr]

nope, you would just make a deepcopy func