ObjectField that can take 2 types of objects

Is there a way to make an ObjectField that can take 2 or more types of objects?

For example, I want to make an ObjectField where you can assign only BoxCollider OR a SpriteRenderer, but no other types.

My idea would be to make the ObjectField itself take any objects of type Object, then in OnInspectorGUI() I check the type of Object, if it doesn't match a type that I want, then... do/dont do something? The problem with that is it the slot itself will appear to accept any type, (you won't get that 'not allowed' icon when trying to assign the slot - it'll look like you can do it, but it just won't work)

 

There is a simpler solution for this. The MonoBehaviours have an OnValidate method which runs when someone change something in the inspector and it does not run in run time. So you can validate whatever is in your exposed variables. The upside: it's simple and very quick to do, the downside is you have limited error message and it's not really fancy like a custom inspector.

 

Alternatively - custom PropertyDrawer + Attribute that will do the same.