How to separate built-in object from user objects?

Question

I'm trying to write a function TypeNameEx which will return a string which, using a call to VarType(), effectively identifies the type of a a (variant) variable, eg VarType 2 returns integer and VarType 3 returns Long.

All is fine until I get to VarType 9 which is an object. I COULD just return Object and be done with it but would rather something more specific. To this end, I have been able to work out how to establish if it is a UNO object and return Object-UNO.

Beyond that, have been unable to make a distinction between one of LibreOffice's built in objects or a user object (as defined in a Class Module). For my own Class Modules, I can give all of my classes a .MyClass property but I cannot do the same for class modules written/supplied by another, is there a way to separate built-in objects from user objects?

I have included my code so far below, it is IsIntrinsicObject which I am stuck on

Function IsIntrinsicObject(ByRef rvarObject As Variant) As Boolean

  'Return the result of a test for a property method or name which a built in
  ' object will have but a user object will not have.
  'As I understand that there no particular property method or name which is
  ' owned by ALL built-in non-UNO objects, this probably boils down ta a 
  ' large Select Case statement which tests a number of things

End Function 'IsIntrinsicObject


Function IsUNOObject(ByRef rvarObject As Variant) As Boolean

  Dim varDummy As Variant

  On Error Goto ErrorHandler
    'If our object DOES have .Dbg_Properties and .Dbg_Methods then
    ' it may still be a none-UNO object, if it doesn't then it 
    ' will fire error 423 if IS a UNO object and error 91 if it is 
    ' any other type of object
    'So here's the belt    
    varDummy= rvarObject.Dbg_Properties
    'And here's the braces - less chance of someone else 
    ' implementing BOTH properties in their own class module than
    ' just the one!
    varDummy = rvarObject.Dbg_Methods
    'Add in some superglue!
    '-If our object is NOT a UNO object this test will fail with
    ' error 438
    varDummy = rvarObject.queryInterface(0)
    IsUnoObject = True
  On Error Goto 0

Exit Function 'IsUNOObject

ErrorHandler: 'Function IsUNOObject
  
  Select Case Err
    Case 423
      Resume Next
    Case 438
      Resume Next
    Case 91
      IsUNOObject = False
    Case Else
      IsUNOObject = False
  End Select 'Err

  On Error Goto 0  

End Function 'IsUNOObject


Function ObjectType(ByRef rvarObject As Variant) As String

  Dim strRet As String
  
  If IsUNOObject(rvarObject) _
  Then
    strRet = "Object-UNO"
  Else 'IsUNOObject(rvobject)
    On Error Goto ErrorHandler
      strRet = "Object-" & rvarObject.MyClass
    On Error Goto 0
  End If 'IsUNOObject(rvarObject)
  
  ObjectType = strRet

Exit Function 'ObjectType

ErrorHandler: 'Function ObjectType

  On Error Goto 0
  If IsIntrinsicObject(rvarObject) _
  Then
    ObjectType = "Object-Intrinsic"
  Else 'IsIntrinsicObject(rvarObject)
    ObjectType = "Object-UnknownUserClass"
  End If 'IsIntrinsicObject(rvarObject)

End Function 'ObjectType


Function TypeNameEx(ByRef rvarVariable As Variant) As String
  
  Dim lngType As Long
  Dim strRet As String
  
  lngType = VarType(rvarVariable)
  Select Case lngType
    Case 0
      strRet = "Empty"
    Case 1
      strRet = "Null"
    Case 2
      strRet = "Integer"
    Case 3
      strRet = "Long"
    Case 4
      strRet = "Single"
    Case 5
      strRet = "Double"
    Case 6
      strRet = "Currency"
    Case 7
      strRet = "Date"
    Case 8
      strRet = "String"
    Case 9
      strRet = ObjectType(rvarVariable)
    Case Else
      strRet = "Unknown"
  End Select 'lngType
  
  TypeNameEx = strRet
  
End Function 'TypeNameEx

Jim K · Accepted Answer · 2025-08-14 18:10:01Z

0

If you're talking about objects such as Collection and FileSystemObject, then from a runtime perspective, there's not really a difference between these and objects from your own class modules.

So the way to do it, which it sounds like you have already surmised, is to test behavior. For example:

Function IsCollection(obj As Object)
    On Error GoTo ErrHandler
    dummy = obj.Count
    obj.Add "test"
    IsCollection = True
    Exit Function
ErrHandler:
    IsCollection = False
End Function

IsIntrinsicObject() would need to do this for each built-in type that you might encounter. However, I only know of a few, so maybe it wouldn't be too much effort to write a function for each.

If one of your modules works like a collection, then such a behavior test wouldn't distinguish between the two.

answered Aug 14 at 18:10

Jim K

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