Passing nulls to a function...How?

[MarkT]

I have an app that pulls data from a database. The data is then passed to a function that manipulates it and returns it as string. The returns from the database could be just about any date type and Nulls are possible. The problem is the code that calls the function can’t be changed to check for nulls. I have set up the function to accept a string as a parameter. This works for everything except nulls. Short of using a variant as the parameter, is there any other way to deal with these nulls?

[Shaggy Hiker]

Why not check for Null before calling the function, then replace it with ""? If you can't alter the function, I don't see what other choice you have. Of course, you could replace it with something other than an empty string, but you pretty much have to replace it with something.

[MarkT]

The data that is being pulled is coming from a compiled dll. I can make it work passing it to a variant and then deal with nulls from there. I was just hoping for something better.

[Shaggy Hiker]

Sorry, I realize that I misread your post. You were clear, and I was confused.

I expect that you're hosed on this. Since a Null is a typeless thing, I doubt that you can use anything but a variant. If it was a number, that would be easier, but I believe it is defined as typeless.

[Eras3r]

str = rec.Fields("whatever")
If IsNull(str) Then str = ""

[Shaggy Hiker]

Yeah, that was my original idea. However, if you re-read his posts, you will realize that he never gets that option.

[BuggyProgrammer]

StrPtr would return 0 on a null string:

Private Sub Command1_Click()
SomeSub vbNullString
End Sub
Sub SomeSub (b As String)
MsgBox StrPtr(b) 'returns 0
End Sub

[MarkT]

Originally posted by BuggyProgrammer
StrPtr would return 0 on a null string:

Private Sub Command1_Click()
SomeSub vbNullString
End Sub
Sub SomeSub (b As String)
MsgBox StrPtr(b) 'returns 0
End Sub

Unfortunately the db returns Null instead of vbNullString. With the code below you see that you never get out of the call procedure.

Option Explicit
 
Private Sub Command1_Click()
    MsgBox SomeSub(Null)
End Sub
 
Private Function SomeSub(b As String) As String
    MsgBox StrPtr(b) 'returns 0
End Function

[crptcblade]

Why avoid the variant? It makes it much simpler when having to deal with a source you can't change...

Private Sub Command1_Click()
    MsgBox Func(Null)
End Sub
 
Private Function Func(ByVal v As Variant) As String
    Func = v & ""
End Function

Tada, no more Null.