How to check if a property is missing or not set (none)

Hello,

I'm trying to figure out how to know if properties, in my case audio clip properties, are missing, meaning the link with the clip has been lost, or if the value is none, meaning the clip was never set.



I tried to use various scripts detecting missing references but none of them can make the difference between Missing and None.

Obviously the editor can tell the difference but I did not find how I can do the same using an editor script.

Any idea ?

Thanks

 

"null" is the C# keyword that corresponds to empty inspector values, so:

if (EndFeedback == null)

{

    Debug.Log("EndFeedback is empty!");

}

Edit: Oh, I think I misunderstood the question. Unfortunately, I don't know the answer to what you were actually asking.

 

I did get valuable help from Unity Slack. you can use reflection to retrieve the string value displayed by the editor :

Code (CSharp):

1. var prop = typeof(SerializedProperty).GetProperty("objectReferenceStringValue", BindingFlags.NonPublic | BindingFlags.Instance);
2.                         var result = (string)prop.GetValue(sp, null);

That way you can check if it's a none or missing value.

 

IIRC, Unity overrides the == operator so that invalid Unity references compare as being equal to "null" even when they are not literally "null". (For instance, a reference to a GameObject that has been destroyed.)

I believe you can use ReferenceEquals to bypass this and check whether the reference is actually null.

 

For future reference, this should do the trick:

Code (CSharp):

1. var isMissing = ReferenceEquals(myVariable, null) ? false : (myVariable ? false : true);

just replace "myVariable" with the variable you want to check.

It basically says:

• Is the reference actually null?
  • Yes: It's not missing, it's just null.
  • No: Something is referenced, is the referenced object "Unity-null"?
    • No: It is not missing.
      
    • Yes: It is missing.

 

I've settled with simply this for cases where I want to know if it's destroyed/missing and for cases I want to know it's really null (i.e. not just destroyed).

Code (CSharp):

1. bool isDestroyed = ((object)var) != null && !var;
2. bool isReallyNull = ((object)var) == null;

Note that (object) needs to be in lower case, to be the alias for System.Object, otherwise you will instead end up casting var to Unity.Object and this code will not work.