Check if BuiltInDocumentProperty is set without error trapping - excel

Question

Task:
My goal is to check if a value has been set in the BuiltInDocumentProperties collection of an Excel workbook.
Amplifying remark:
I know that some doc properties items never show a value in Excel as they
belong to ms word or ppt applications (e.g. item 15 'Number of words', item 25 'Slides' ...).
On the other hand some properties have only occasional values in case of first use:
item 10: 'Last print time'
item 12: 'Last save time'
Of course one can do that by error trapping:
Example Code with Error trapping:
Sub test_showDocPropValue()
' Name of built in doc prog
Dim propName As String
' a) Choose builtin doc prop disposing about a set value, such as 'Author', 'Category', ...
' propName = "Category"
' b) Choose builtin doc prop of another ms application
' propName = "Number of pages"
' c) Choose doc prop with occasionally set values
propName = "Last print time"
' Show result
MsgBox propName & " = " & showDocPropValue(propName), vbInformation, "BuiltInDocumentProperties"
End Sub
Function showDocPropValue(ByVal propName As String) As Variant
Dim prop As Object
Dim ret
' Built in Doc Props collection
Set prop = ThisWorkbook.BuiltinDocumentProperties
' Error trapping
On Error Resume Next
ret = prop(propName).Value
If Err.Number <> 0 Then
ret = "(No value set)"
Debug.Print Err.Number & ": " & Err.Description
End If
' Return
showDocPropValue = ret
End Function
My Question:
For principal reasons I'd like to know if there is a straightforward method to get builtinDocumentProperties values avoiding error trapping
Additional hint
Just to complete the theme by showing methods without error trapping within CUSTOM doc props, you can easily check for the existence of such items with the following code:
Private Function bCDPExists(sCDPName As String) As Boolean
' Purp.: return True|False if custom document property name exists
' Meth.: loop thru CustomDocumentProperties and check for existing sCDPName parameter
' Site: <http://stackoverflow.com/questions/23917977/alternatives-to-public-variables-in-vba/23918236#23918236>
' cf: <https://answers.microsoft.com/en-us/msoffice/forum/msoffice_word-mso_other/using-customdocumentproperties-with-vba/91ef15eb-b089-4c9b-a8a7-1685d073fb9f>
Dim cdp As Variant ' element of CustomDocumentProperties Collection
Dim boo As Boolean ' boolean value showing element exists
For Each cdp In ThisWorkbook.CustomDocumentProperties
If LCase(cdp.Name) = LCase(sCDPName) Then
boo = True ' heureka
Exit For ' exit loop
End If
Next
bCDPExists= boo ' return value to function
End Function

Answer 1

I think there is not a straightforward way of doing it -- this is a Collection which doesn't have an easy way to test for existence of an item (versus a Dictionary.Exists method, or using a Match function against an array, etc.). Apart from error-trapping (which seems pretty straightforward IMO) you are left basically to use brute-force iteration over the collection's items, checking the .Name property for equivalence.
This is a approach similar to what you have with the CustomDocumentProperties to avoid the Error-handling if desired (although I see nothing explicitly wrong about that approach). Modified your showDocPropValue function and added an additional GetDocProp function to be used in tandem. This should work with your test case:
Function showDocPropValue(ByVal propName As String) As Variant
Dim prop As Object
Dim ret
' Get the BuiltInDocumentProperty(propName) if it exists
Set prop = GetDocProp(propName)
If prop Is Nothing Then
ret = "(No value set)"
Else
ret = prop(propName).Value
End If
' Return
showDocPropValue = ret
End Function
Function GetDocProp(ByVal propName$)
' returns the BuiltInDocumentProperties(propName) object if exists, else Nothing
Dim p As Object
Dim prop As Object
Set prop = ThisWorkbook.BuiltinDocumentProperties
For Each p In prop
If p.Name = propName Then
Set GetDocProp = p
GoTo EarlyExit
End If
Next
Set GetDocProp = Nothing
EarlyExit:
End Function
Personally, I would use this version instead (error handling in the GetDocProp function):
Function GetDocProp(ByVal propName$)
' returns the BuiltInDocumentProperties(propName) object if exists, else Nothing
Dim ret As Object
On Error Resume Next
Set ret = ThisWorkbook.BuiltinDocumentProperties(propName)
If Err.Number <> 0 Then Set ret = Nothing 'just to be safe...
Set GetDocProp = ret
End Function