[BUG] CheckVariable broken?

[guyboots_thunderbroParticipant]

I have a Transform on my Blackboard called “Target” that is set to a GameObject’s transform. When the GameObject is destroyed in the scene, the Blackboard correctly recognizes that “Target” is now null.

However, the CheckVariable<T> condition transition that compares “Target” to NONE thinks that “Target” is not null.

Under the hood, in CheckTransform<T>.OnCheck(), valueA.value evaluates to "null" (a string with the contents of “null”) rather than null, which causes this problem.

I’m on NodeCanvas 3.0.5.

[GavalakisKeymaster]

Hey,

The problem stems from how Unity treats UnityEngine.Objects when they are deleted. I have added a special case in the CheckVariable to handle this situation and attached the fixed package for you here.

Let me know if that works for you.

Thanks 🙂

[guyboots_thunderbroParticipant]

> Let me know if that works for you.

Seems to work, thanks!

I notice that ObjectUtils.AnyEquals is also used in a few other places in the codebase — I haven’t seen any bugs from it yet, but do they need the same fix?

[GavalakisKeymaster]

I will run a code review regarding this and let you know (as well as fix it) if anything comes up 🙂

Thanks!

[guyboots_thunderbroParticipant]

Confirming that some other areas that use ObjectUtils.AnyEquals, such as BBParameter.isNull, are affected by this.

[GavalakisKeymaster]

Thank you for the report.

The source of the issue mostly comes from the fact that when a Unity object is destroyed, it is still kept referenced (which is normal). A more proper workaround fix for this would be to please open up ObjectUtils.cs and change method AnyEquals to this:

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public static bool AnyEquals(object a, object b) {               //regardless calling ReferenceEquals, unity is still doing magic and this is the only true solution (I've found)             if ( ( a is UnityEngine.Object || a == null ) && ( b is UnityEngine.Object || b == null ) ) {                 return a as UnityEngine.Object == b as UnityEngine.Object;             }               //while '==' is reference equals, we still use '==' for when one is unity object and the other is not             return a == b || object.Equals(a, b) || object.ReferenceEquals(a, b);         }

This should handle the null checks with unity objects better and of course for all cases AnyEquals method is used (thus no need for the first fix I sent you any longer)

Let me know if that works for you.
Thanks 🙂

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