strictly typed vi refnum in a class? in Object-Oriented Programming Posted January 21, 2014 · Report reply Figured it out. My 'handler' VI has an input of type 'system class' and I was trying to add the strictly typed refnum of the handler to that 'system class'. Looks like I will have to find an acceptable hack to fix this. I am thinking of passing the class to the handler as a generic reference and then casting it in the handler to the proper type. Any better ideas?