Table.insert is removing values?

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#1

I’m trying to use table.insert to add values to a pre-made table.

local drops = {
    [3] = "Sword",
    [6] = "Sword +1",
    [7] = "Shield"
}

for i = 1, 2 do
    table.insert(drops, i, "Gold")
end

for i = 4, 5 do
    table.insert(drops, i, "Gold")
end

print(drops)

However, any index before the pre-made index is being removed (ex table.insert(drops, 2, “Gold”) will remove [3] = “Sword”) and index 6 and 7 are being shifted up by 1, leaving index [3] and [6] “void”, or nil.
This is what the output shows:
image

and can be tested using this code:

local test = {
    [3] = "Three"
}

table.insert(test, 2, "Two")

print(test) -- [3] = "Three" is suddenly missing

I’ve already thought about using table[index] = value instead as shown below which works properly, but I was wondering if this is a problem with my coding, roblox engine, or the function itself. Can anyone else get the same result, or give me insight on this? If this is really a bug, then could someone else report this issue because I do not have permission to post there.

local drops = {
    [3] = "Sword",
    [6] = "Sword +1",
    [7] = "Shield"
}

for i = 1, 2 do
    drops[i] = "Gold"
end

for i = 4, 5 do
    drops[i] = "Gold"
end

print(drops)
2 Likes
#2

I think the Roblox table.insert() documentation could lead one to not realize
the shifts–See:
https://www.lua.org/manual/5.1/manual.html#pdf-table.insert

Probably contributing to your confusion is how # in Lua actually works–
It often confuses people, as what it actually does is not what one might think:
https://www.lua.org/manual/5.1/manual.html#2.5.5

“I’ve already thought about using table[index] = value instead as shown below which works properly…”
Yes do this instead, as this appears to be what you are trying to accomplish.

#3

I know that shifting works properly in Roblox:

local tab = {
    [4] = "Hi"
}

table.insert(tab, 4, "New")

print(tab) -- [4] = "Hi" has been shifted to [5] = "Hi" and [4] = "New" now exists

The problem here is that it is shifting the value when i = i - 1 which somehow also deletes the value.

local tab = {
    [4] = "Hi"
}

table.insert(tab, 3, "New")

print(tab) -- [4] = "Hi" has been shifted to "void" and no longer exists. [3] = "New" now exists by itself.

I do not believe this is intended behavior, or am I missing something here?

1 Like
#4

I’m not good at tables but is your script replacing tables Edit: I don’t think it’s possible that happens

#5

Or wait, is it because [3] = nil so when table.insert is called, [3] = nil is being shifted to [4] = “Hi” which causes it to become nil? That makes much more sense to me.

#6

Nvm so it’s possible your replacing the tables with nil so try to fix that

#7

When you have a table that’s like an array, but really isn’t, it can be quite a mess to deal with.
A proper array starts at index 1 and has no holes in it.