Mono Upgrade Using the null-conditional operator with components using .NET 4.x

For example, with the code

GetComponent<AudioSource()?.Play();

I will get a missing component exception if there is no AudioSource on the game object.

I would expect the ?. null-conditional operator to guard against this exception. Is this a bug or am I missing something?

 

https://blogs.unity3d.com/2014/05/16/custom-operator-should-we-keep-it/

basically, 2 things happen:
- UnityEngine.Object overloads the == operator, so that "== null" returns true if the object is missing or has been destroyed, but the variable does not contain a real null
- in the editor, GetComponent<>() returns a "fake null" object if the component does not exists

meanwhile, the "??" and "?." operators check for real null, bypassing the overload and basically doing a hard "ReferenceEquals".
this results in the "?." check to pass (managed object is not null)
finally, Unity throws MissingReferenceException from C++ when you call AudioSource.Play() on a null (according to Unity) object

 

Thanks for clarifying! This explains why the behavior is happening. I guess my follow-up question is, should that be what happens? It would be nice to use the ?. operator without remembering esoteric special cases.

 

the main problem is that an UnityEngine.Object can be destroyed, and there is no way to magically set all references to null every time you destroy something (the closest thing they could do is basically a full GC collect).

you could create your extension method that does the manual check and returns a real null when you access the object, then you could do

GetComponent<AudioSource>().SanityCheck()?.Play()

. (protip: extension methods can have a null

this

because they are actually static methods with syntax sugar)