ChildAdded with Tables?

Help and Feedback Scripting Support
#1

Hello,

How would I use ChildAdded (or something of the sort) for tables? I’ve asked other people but they told me to use loops, which clogs and isn’t that good.

(Example of a loop that I DON’T want to use due to it being a loop, laggy, etc.)

local Table = {};

while wait() do
  if #Table then
    print(Table[#1] .." is a new value of our table.");
  end;
end;
1 Like
Get When Item is Added to a Table
#2

Can you explain more about this table and what it is? When are you adding new stuff to the table?

1 Like
#3

Yeah, I’m basically in a situation where if I use a function in an event, the function doesn’t run because of the weird environment the event is in. So I have to use tables, but I can’t constantly check the tables with loops or else it’ll make the script performance bad.

I heard I could use __newindex, but I’ve never seen it being used before. Would you happen to know where I could find an example?

#5

I don’t need to see the contents of the table, I just need an event that fires once something gets added to the table.

#6

Donno how helpful would this be but before you add a value to the table, you could pass it through a value object then track it using the “.Changed” signal.

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#7

I’d need to create a function for that and in this case I literally can’t use a function. For some reason, when I create a function that only prints, it works, but when I create a function for a gui for example, it literally does not work.

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#9

GetChildren just returns the children of the table. I don’t want the contents of the table, I wanna know when they get added to the table, like ChildAdded.

#10

So, to use something similar to child added, maybe use an if statement. Something like this:

if table.insert(Table, "value") then
 -- do something
end
1 Like
#11

Your solution is metatables, specifically the __newindex metamethod. __newindex fires whenever a blank index gets set to something, which is exactly what you want. There are plenty of threads on metatables, so I don’t want to explain them, however here is the developer hub article on them if you want: https://developer.roblox.com/en-us/articles/Metatables.

Here is a code example for what you want:

local Table = {}

setmetatable(Table, {
    __newindex = function(_, index, value)
        print(tostring(index) .. " has been added and set to " .. tostring(value))
    end
})

--Examples:
table.insert(Table, "message") --> 1 has been added and set to message
table.insert(Table, 5) --> 2 has been added and set to 5
Table[3] = 0 --> 3 has been added and set to 0
Table[2] = 10 --nothing gets output, as the key 2 has already been set to something
Table.whatever = "hi :)" --> whatever has been added and set to hi :)
Table.whatever = "bye :(" --nothing gets output, as the key whatever has already been set to something
5 Likes
#12

The solution is almost never metatables. You’re not wrong, but it is generally a better idea to just call a function when you change the table. Or make a custom function to do both.

2 Likes
#13

he meant he wants the code to print a new element of the array when it is added to the table

1 Like
#14

That is actually what the linked post shows. I made the post titled “adding a changed event to a table.”
However, my method covers both ChildAdded and ChildRemoved in one single event.

What you’re looking for is metatable.__newindex. To entirely understand this, I recommend looking into Lua metatables a bit. In a sense, __newindex will fire when a new entry (with an index that hasn’t existed yet) is made.

1 Like
#15

Yes, I’ve been working with metatables for about a week or so but I’ve never really understood it to the fullest point. Thank you.

1 Like