How check if a resource exists before instantiating

News & General Discussion
1

What is the correct way to check that a resource exists before instantiating it? Sometime I delete resources and forget to remove the instantiation from all my scripts

I’m using something like this,

Arrow = (GameObject)Instantiate(Resources.Load("Props/Arrow"),transform.position, Quaternion.Euler(new Vector3(0, 90, 0)));

Want to make sure that the Arrow resource is there before I try to Instantiate it.

Thanks,

V

2

From the docs on Resources.Load:
This method returns the asset at path if it can be found, otherwise it returns null.
However using such a check for your usecase has a lot in common with covering a large gap in a wall with newspaper.

3

I wouldn’t check for this at runtime. You should search your codebase and remove the code that references these resources.

1 Like
4

Not really, let’s say I’m instantiating some cosmetic stuff that is isn’t important, then delete the prefab for what ever reason but forget to find the code that instantiated it. I have thousands of prefabs, lots not instantiated. It’s just a check like any other check we do a thousand times, if (something != null) then do whatever…

5

hmm, so the answer is no? I would, and could and should… but I forget as I am lowly human…

6

Which is precisely why you should avoid writing code that depends on “magic strings”. Instead you should write code that moves the responsibility from you to the compiler and/or the game engine.

https://en.wikipedia.org/wiki/Magic_string

If that’s not possible you should minimize the number of locations that it can be in. One way to do this is a static class with methods like the following:

public static GameObject Arrow()
{
    var resource = (GameObject)Resources.Load("Props/Arrow");
 
    if (resource == null)
        Debug.LogError("Arrow prefab not found.");

    return resource;
}

Then you can just instantiate it like this:

arrow = Instantiate(MyStaticClass.Arrow(), transform.position, Quaternion.Euler(new Vector3(0, 90, 0)));
7

Thanks Ryiah