What happens if player leaves in middle of running a function?

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#1

I’m probably overthinking this, i’m not talking about anything like a datastore function or a remote function that many sources say to use a pcall for.

I’m going to have a function that loops through every player on a team of 10 players changing the teams and leaderstats of a bunch of players at once.

It looks something like

for i, Player in pairs(TeamB:GetPlayers()) do
Player.Team = TeamA
Player.leaderstats.points:Destroy()
end

What happens if a player leaves as a change is happening? If the script crashses then the whole server becomes useless because the script handles the round-based game im making. Is having a single script controlling a round-based game a bad practice since something crashing could take out the whole server?

I’m still quite new, if any of my questions are vague or don’t make sense please let me know.

#3

Actually, ipairs breaks the loop if it hits a nil value somewhere.

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#4

This is what i’m confused about. I don’t wanna break the loop if I hit a nil right? I have to get everyone’s team swapped.

#5

Oh lol that’s embarrassing, thanks for the correction.

Edit: adding a conditional check if player ~= nil is still going to have the effect you are looking for.

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#6

I should have been doing that but I was being lazy and rushing >_<

#7

You could check if the Player exists every time the loop runs.

for i, Player in pairs(TeamB:GetPlayers()) do
if Player ~= nil then
Player.Team = TeamA
Player.leaderstats.points:Destroy()
end
end

but I think if the player left at just the right time it could still break this function. If you want to avoid all possibility of breaking it I believe you could use a pcall. Correct me if I am wrong though.

#8

It depends on what kind of a function you’re running, how expensive it is and how long it’ll take to complete. Your function probably won’t be slow enough that it iterates over a player who left while the loop is running. Regardless though, functions usually error or cancel in the case that a player leaves while it’s running.

It’s important that you pcall error-bound code (especially anything that directly or indirectly is a web call) and don’t assume that your code will always produce truthy results for any kind of indexing (by direct indexing, FindFirst/WaitForChild, etc).

#9

I’d suggest doing a pcall to check if the change was successful:

for i, Player in pairs(TeamB:GetPlayers()) do
	if Player then
		local plr_name = Player.Name or "unknown"
		local success = pcall(function()
			Player.Team = TeamA
			Player.leaderstats.points:Destroy()
		end)
		if not success then
			warn("Player "..plr_name.." left while processing!")
		end
	end
end
1 Like