Quick questions about metables

[strong orbit]

Hey i was just wondering can someone explain to me howw the __index function in metables truly works ? Does it just fires EVERYTIME i index something in my table or only when i index something to initialize a variable ?

myvariable = table[index] works ?

table[index] +=5 works ?

[knotty void]

would like an explanation on this as well, don't mind this message

[exotic valley]

Only if its nil :) but yes it works everytime you index it

[rocky halo]

Basically you know when you do something like humanoid:TakeDamage

If you have a table and uou create a function

You can assign that to the table

For example if the table = player = {health = 100}

And hsve this function

Local function toonehp(amount)

Then you can do metatable(player,__index = tooonehp)

And you can fire this:

Player:toonehp(99)

Keep in mind that when using : the self is already a variable and is set as the table (in this case the player)

[rotund herald]

close but no cigar. This is not quite what the metamethod does. This can also be achieved by just adding functions to dicts:

local ExampleDict = {};

ExampleDict["ExampleMethod"] = function() return "ExampleString" end

print(ExampleDict:ExampleMethod())

anyways, @strong orbit @knotty void metatables are just a way to connect metamethods to a table.
Metamethods are internal events that listen for certain actions to work. E.g. __index fires when you index a table key that does not exist in said table (which is what roamer used to then connect that to another table), but there are many other metamethods, which you can read about here https://create.roblox.com/docs/luau/metatables#metamethods

There are also some optimization techniques that use metatables, to simply attach references to different tables to a table, instead of copying the entire table for every table that has to keep those references

[rocky halo]

Wth

Wheres the metatable function

[rotund herald]

In the code? there is no need for it. I just added the function straight into the dict instead of into a table, then making an index nil reference said table

[rocky halo]

No way

Thats cool

[rotund herald]

-- alternative (and more common) way of adding functions to dicts
function ExampleDict.ExampleMethod2()
    return "ExampleString2"
end

Both work fully without metamethods

;compile

local ExampleDict = {};

ExampleDict["ExampleMethod"] = function() return "ExampleString" end
function ExampleDict.ExampleMethod2()
    return "ExampleString2"
end

print(ExampleDict:ExampleMethod())
print(ExampleDict:ExampleMethod2())

[grizzled rampart]

Program Output

ExampleString
ExampleString2

dadjokesaregreat | lua | lua-5.4.7 | wandbox.org

[rotund herald]

The reason why folks use index for this effect is to save on ram. As then you can just save a singlular reference to the functions instead of having to create new functions for every table (purely in memory, not in the script itself of course)