Differentiate between 'null' and 'missing' references in script?

Is there a way to tell the difference in script between an object reference that's null (it has never been assigned) vs one that's missing (the object that was assigned has since been destroyed)? The default inspector can tell the difference - it says 'Null' or 'Missing' respectively - but how?

 

an object that has been destroyed can still have GetInstanceID() called on it, even though a null comparison equates to true (the equality operator for null is overridden I believe), could you use the GetInstanceID() result to differentiate how you want?

 

If I call 'unknown.GetInstanceID()', and unknown is null, that would throw an exception. I could wrap it in a try/catch, I suppose? So maybe something like this?

Code (csharp):

1.  
2. bool IsMissingReference(UnityEngine.Object unknown) {
3. try {
4. unknown.GetInstanceID();
5. return false;
6. }
7. catch (System.Exception e) {
8. return true;
9. }
10. }

 

As I understand it, that ought to work, have you tried it?

I was trying to find a blog post I read recently, which I thought you might find useful, where one of the devs was discussing their reasoning behind overriding the null equality operator, and why they probably wouldn't change it. But as usual I can't find it now

 

I'd enjoy reading the reasoning behind overriding the equality operator, if you stumble across it again.

 

Found it

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

 

Code (csharp):

1.  
2. var b = object.ReferenceEquals(obj, null);
3.  

This method will actually test if null, as opposed to testing if destroyed.

So it will return true if the thing is actually null, not just dead.