Creating new objects in the Update() method

Question

I read somewhere that I shouldn't create any new object instance in the Update() method of the game engine, because this will lead to wake Garbage Collector up and decrease performance, but sometimes I see in some tutorials that they use new keyword in unity Update() method! Is this okay? And unity will handle this in someway, or no?

Answer 1

This is a confusing thing for new C# programmers.

Is this okay?

The answer to this depends on the datatype that you using the new keyword on. This is basically value type vs reference type. See the link at the end of this answer for more information on this.

• If it is a class, then don't use the new keyword on it in the Update function. Use Object Pooling or you will be creating new Object every frame. Yes, this is costly.
• If it is a struct, you can freely use the new keyword on it in the Update function without.

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You may have seen a code like this in the Update function:

Vector3 vec = new Vector3(0, 0, 0);

That's fine because Unity's Vector3 is a struct not a class.

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Another example is this in the Update function:

GameObject obj = new GameObject("MyObject");

This is bad because GameObject is a class. You are creating a GameObject each frame. Do this once in the Start function then re-use it. You can also use object pooling.

Notice the circled text in red color, you can use that to determine if the API you are using is a class or a struct.

Here are other things to know:

1.C# value type vs reference type

2.is there a point in recycling value types unity

3.What's the difference between struct and class in .NET?

4.Object Pooling in Unity

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Note that this answer focuses on using the new keyword in Unity as mentioned in your question. There are still other things that can allocate memory without even using the new keyword. Examples includes using the param keyword in a function parameter, returning an array in a function, using yield return 0 instead of yield return null.

And unity will handle this in someway, or no?

The only one that can answer this question is the device you are running this code on. Usually, you get some hiccups on mobile devices due to GC running. Object Pooling is very important on mobile devices.