Variable not defined in VBA script - vba

Question

I'm getting into the good habit of using Option Explicit at the top of all my MS Access VBA scripts. However, for this function it's giving me a Variable not defined error highlighting the line that begins with Set objSysInfo =
Public Function GetUser(Optional whatpart = "username")
Dim returnthis As String
If whatpart = "username" Then GetUser = Environ("USERNAME"): Exit Function
Set objSysInfo = CreateObject("ADSystemInfo")
Set objUser = GetObject("LDAP://" & objSysInfo.UserName)
Select Case whatpart
Case "fullname": returnthis = objUser.FullName
Case "firstname", "givenname": returnthis = objUser.givenName
Case "lastname": returnthis = objUser.LastName
Case Else: returnthis = Environ("USERNAME")
End Select
GetUser = returnthis
End Function
Might I be missing a specific reference?

Answer 1

Option Explicit forces you to declare all variables.
This means you must declare all variables you're using, otherwise your code won't compile - as you've noticed.
You declared local variable returnthis as a String, using the Dim keyword:
Dim returnthis As String
That's how you declare a local (procedure scope) variable.
You could declare variables at module scope using the Private keyword (Dim works as well, but better keep Dim for locals)
Option Explicit
Private foo As Object
How you scope variables depends on where you're using them - if a variable is only ever used in one single procedure, then it's better to scope it to that procedure and declare it as a local variable.
In this case you have objSysInfo and objUser that aren't declared anywhere.
Dim objSysInfo As Object
Dim objUser As Object
I know we're not on Code Review, but while we're here there are other issues with your code:
The return type of the function is implicitly Variant. Append As String to the end of the function's signature.
The optional parameter whatpart is implicitly Variant as well, and implicitly passed ByRef, but you only need to read it, not write and return to the caller - so declare it Optional ByVal whatpart As String = "username".
Prefer the Environ$ function over Environ - both do the same thing, but Environ returns a Variant, that you're implicitly converting to a String - best use Environ$ and work with a string from the start.
Instead of relying on magic, hard-coded strings, use an Enum value and Select Case over the possible legal values:
Public Enum NamePart
EnvironmentDefined
FullName
FirstName
LastName
End Enum
The full code could look like this:
Public Enum NamePart
EnvironmentDefined
FullName
FirstName
LastName
End Enum
Public Function GetUserName(Optional ByVal part As NamePart = EnvironmentDefined) As String
Dim result As String
Dim sysInfo As Object
Dim userInfo As Object
If Namepart = EnvironmentDefined Then
GetUser = Environ$("USERNAME")
Exit Function
End If
Set sysInfo = CreateObject("ADSystemInfo")
Set userInfo = GetObject("LDAP://" & sysInfo.UserName)
Select Case part
Case FullName
result = userInfo.FullName
Case FirstName
result = userInfo.GivenName
Case LastName
result = userInfo.LastName
Case Else
result = Environ$("USERNAME")
End Select
GetUserName = result
End Function
Note, I didn't include a GivenName enum member, since it's redundant; calling code can do this:
Dim value As String
value = GetUserName(FirstName)