When is it appropriate to use :WaitForChild()

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#1

First of all i know that there a billion topics about this and i’ve read a lot of them but the answers are kind of vague. I already know how they work and use them all the time. But one of the reasons i use them the most is to make sure that an instance has already loaded into the game, and i’m afraid i’m using them when i shouldn’t.

I want to know:

1: Do i have to use :WaitForChild() for literally every single instance outside of ReplicatedFirst? Because i have multiple scripts that run at the start of the game and some stuff might not be loaded by then.

2: After i use :WaitForChild() in an instance, do i have to use it again for their children?

Ex: ReplicatedStorage > Folder > Module

local ReplicatedStorage = game:GetService("ReplicatedStorage")
local Folder = ReplicatedStorage:WaitForChild("Folder")
local Module = Folder:WaitForChild("Module")

Edit: I’m only talking about instances that are on the game when it starts, not the ones that are created afterwards

#2

When its possible that the thing you want could still be loading, this is:
1 Basically always when on the client
2 On the server only when the item is being added by another script which could wait() in the middle of its job.

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#3

Not really. You can assume that the children exist often. However, If a child is added after the fact, say a script clones a part and parent’s it under a models instance and you are looking for that part, thats when you should avoid what I said above and look for it using WaitForChild().

Yes? No? It doesn’t really matter. Some people will have strong opinions and there are times where WaitForChild should absolutely used. My rule is this. If your working on a big game and have a lot of instances in workspace, you should use WaitForChild on workspace objects as often workspace objects if I remember correctly are likely last to load.

Now if your experiencing Errors, Or using the Error reporter that shows the top 50 errors/warnings and an error is coming becase an instance doesn’t exist, then you should abolutely use WaitForChild(). Personally It just depends on the game and I wouldn’t worry about it too much

#4

I can assume? That’s not a reassuring answer, i want to know for certain, else my script might error and my game breaks.
I’m not talking about instances that are made after the game starts by the way, i’m talking about the ones that i make on the studio.

Why does it not matter?

I know i can go back and fix my mistake later if something goes wrong, but i made this topic because i want to know how to not make those mistakes in the first place.

#5

It really depends on what you need it for (which isnt a lot), but a good rule of thumb is to use it when you can ensure the object exist/will exist within a certain time frame, as it has the ability to halt code when the object is not found because of a timeout.

:WaitForChild() in standard practice, should only ever be used on the Client when you can ensure the object exists. Unlike the Server which has everything loaded in, the Client needs to load in everything that is able to be Replicated for it, if your code fires very early, you will likely run into errors indicating that the object doesnt exists yet, which is where :WaitForChild() comes in, which waits until it finds the object, or until it reaches the timout.
Which in essense

  1. Object Loads in

  2. :WaitForChild() finds this item

  3. Code functions as intended

Bad usages of :WaitForChild() that I can think of are:

  • Server Usage
    The Server will always have everything loaded in, Waiting for something that is already existing is pointless, and just uses more resources, aka bloat.

  • Sanity Checks
    If you are just checking if an Object exists, :WaitForChild() is an awful way of doing it as explained earlier, In order to perform a proper Sanity check with Instances, you can use :FindFirstChild(), difference being that it does not yield, and does not return an error if the object doesnt exist, with it instead returning nil, Because it returns nil, we can check for the Condition if Object ~= nil then, to perform this sanity check.

Most likely, but for a good reason.

ReplicatedFirst, is the first thing the Client will Fire Code from (Its in the name lol), before the Game has loaded in, which is how we are able to create stuff like loading screens with seemless transitions, and preload our games.

Because it fires so early, very little would have been replicated, besides the Services provided to you, so in order to ensure that you are grabbing an object outside of ReplicatedFirst, you need to wait for it to exist, and as expected, :WaitForChild() does this job perfectly, however if you wait long enough using some code that maybe yielded for a while, you might not have to use it, as by that point it should have already loaded in.

Most likely not , but if any errors occur over it not existing (Its pretty rare for me, but i cant say the same for everyone else), then I would say use it, but this is something I dont see happening to often, so its a precaution worth taking.

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#6

Use it whenever you’re unsure of an object’s existence and you know it is going to exist at some point. Use FindFirstChild when you’re just checking for the existence of an object.

#7

one last question, if i’m on the client, and i use :WaitForChild() to get a function that maybe hasn’t loaded in yet, do i have to use :WaitForChild on their children too?

#9

:FindFirstChild() just looks for a valid child immediately.
:WaitForChild() is for when you want to yield (stop) the script until a child of that name becomes available.

#10

I use :WaitForChild() for almost everything. I know I probably could use :FindFirstChild() for a lot of things in my code, but I feel like :WaitForChild() prevents most issues. Of course, this isn’t always the case for WaitForChild(), as the built-in system that Studio has does warn you that an infinite yield is possible in some cases.

Overall, though, there is no appropriate nor inappropriate time to use :WaitForChild(). It’s there for a reason, and can be used whenever you want to use it. Don’t feel comfortable with :FindFirstChild()? Use WaitForChild(), as it yields the code until an instance is found. However, using WaitForChild() for something that you want to happen immediately is bad. :WaitForChild() actually counts as a task.wait(), and will slow your script down by 1 frame each time :WaitForChild() is used.

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#11

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