Absolute BEST way to circumvent "Something unexpectedly tried to set the parent of instance to NULL"?

[Disunize (Digitality)]

In various scenarios using things such as ChildAdded or DescendantAdded, and then immediately modifying the Parent property of the instance, or even destroying the instance, I have come across this error:
“Something unexpectedly tried to set the parent of instance to NULL”

What is the absolute best way to circumvent this error that would work in any scenario where I would need to immediately change the Parent of an instance after being changed beforehand?

For example, if I needed to immediately destroy any instance added into a specific object, I would do something like this:

instance.ChildAdded:Connect(function(child)
    child:Destroy()
end)

Doing so would result in the error.

Any help in combatting this error would be greatly appreciated!

[ReloadedO (Reloaded)]

To circumvent this you must introduce a slight delay in the script. Like adding task.wait()

[RobloxHasTalentR (LOLLLLLLLLL_1)]

firstly use wait() before modifying Parent

Connect to a different event:

Instead of ChildAdded, consider using DescendantAdded if you only need to act on direct children

[apictrain0]

I think RunService.Heartbeat:Wait() may work just a little bit better but I think both will do

[RobloxHasTalentR (LOLLLLLLLLL_1)]

instance.ChildAdded:Connect(function(child)
  wait() --wait to allow the child added event to complete
  child.Parent = someplaceElse
end)

[argubarguilija222]

Please fact check before copy-pasting advice from chatGPT.

[StrongBigeMan9]

@Disunize

For example, if I needed to immediately destroy any instance added into a specific object, I would do something like this:

instance.ChildAdded:Connect(function(child)
    child:Destroy()
end)

Doing so would result in the error.

Without adding any sort of delay, the object would be destroyed on the same frame as it was added, which, from my understanding, is what results in that error.

Using task.defer() on the :Destroy() call would consistently give it enough time (until the *next resumption cycle), to avoid that error from occurring.

*The documentation for task.defer() references this announcement on the developer forum for an explanation of resumption cycles.

Example

instance.ChildAdded:Connect(function(child)
    task.defer(child.Destroy, child)
end)

-- OR

instance.ChildAdded:Connect(function(child)

    task.defer(function()
        child:Destroy()
    end)

end)

That implementation was offered as an example by a Roblox staff member upon the release of the task library:

Task Library - Now Available!

Here’s a really easy to understand use case: object.ChildAdded:Connect(function(child) if someCondition(child) then --> Kaboom! child:Destroy() --> Destroys on the same frame that the child was added! -- (there was no non-hacky way to accomplish this before) task.defer(child.Destroy, child) end end) I’m expecting to task.spawn to be much more widely used, but I think you’ll find that use cases for task.defer do come up reasonably frequently,…

[ReloadedO (Reloaded)]

Yeah, I was wondering if it was chatgpt also.

[Den_vers]

@StrongBigeMan9

instance.ChildAdded:Connect(function(child)
    task.defer(child.Destroy, child)
end)

I wouldn’t recommend this way of calling :Destroy(). It’s slower than just:

task.defer(function()
    child:Destroy()
end)

I benchmarked both of them using this code:

local function benchmark1()
	local a = Instance.new("Part")
	local b = os.clock()

	a.Destroy(a)

	return os.clock() - b
end

local function benchmark2()
	local a = Instance.new("Part")
	local b = os.clock()
	
	a:Destroy()
	
	return os.clock() - b
end

for g = 1, 100 do
	local avg1 = {}
	local avg2 = {}

	local sum1 = 0
	local sum2 = 0

	for i = 1, 100 do
		table.insert(avg1, benchmark1())
		table.insert(avg2, benchmark2())
	end

	for _, avg in avg1 do sum1 = sum1 + avg end
	for _, avg in avg2 do sum2 = sum2 + avg end

	sum1 /= #avg1
	sum2 /= #avg2

	print(sum1 > sum2)
end

And here are the results:

It may be a fancier way of doing it, and being faster to write, but I always use the latter, it’s faster.

[RobloxHasTalentR (LOLLLLLLLLL_1)]

Yea I use the AI to mostly help or editing something but it works mostly with all the things I tested with such as turning a model into rainbow on touch even with meshes

[StrongBigeMan9]

@Den_vers

@StrongBigeMan9

instance.ChildAdded:Connect(function(child)
    task.defer(child.Destroy, child)
end)

I wouldn’t recommend this way of calling :Destroy(). It’s slower than just

Ah, I had included that way as one of the options because it was what was specifically mentioned by a Roblox Staff member when task.defer() was introduced.

@Den_vers

And here are the results:

It may be a fancier way of doing it, and being faster to write, but I always use the latter, it’s faster.

Thanks for creating a benchmark of it! Had no idea about the speed difference between the two