Finding the type of object in MapBasic (MapInfo)

Question

I am trying to write a MapBasic function to check whether or not an object can be used with the Overlap/AreaOverlap functions - I need to tell whether it's a closed shape or a line/arc/point/text object.

I have two questions.

1. Is there an existing function that will do this?

2. Why doesn't this work?

   Function IsObjectRegion(ObjAlias As Alias) As Logical
       Dim ObjectType As SmallInt
       Note OBJ_TYPE_POINT    ' This popup is displayed correctly
       Note "Crash Now."      ' This doesn't display. 
                              ' Instead you get an error that says "could not convert data".
       ObjectType = ObjectInfo(ObjAlias, OBJ_INFO_TYPE)
       Do Case ObjectType
           Case OBJ_TYPE_REGION
               IsObjectRegion = True
               print "Object WAS a region"
           Case OBJ_TYPE_RECT 
               IsObjectRegion = True
               print "Object WAS a region"
           Case OBJ_TYPE_ROUNDRECT 
               IsObjectRegion = True
               print "Object WAS a region"
           Case OBJ_TYPE_ELLIPSE
               IsObjectRegion = True
               print "Object WAS a region"
           Case Else
               IsObjectRegion = False
               print "Object was NOT a region"
       End Case
   End Function
   

Answer 1

I think you need to be passing an object variable into the function, not an alias which is just a column reference.

Function IsObjectRegion(selObj As Object) As Logical
Dim ObjectType As SmallInt

ObjectType = ObjectInfo(selObj, OBJ_INFO_TYPE)
Do Case ObjectType
...

If you wanted to test this out with the currently selected object, you could call the function like this:

    Dim test As Logical
    Dim testObject As Object
    testObject = Selection.Obj
    test = IsObjectRegion(testObject)

    Note test

This should return True/False.

James