How Many Parameters ?

Posted on 2002-07-25
Last Modified: 2010-05-02
I have a function with 2 optional paramters

Public Sub ShowContact(ID As Long, Optional lClientNum As Long, Optional bShowButtons As Boolean = False)

The value of lClientNum can = 0 at times

Sometimes I dont need the lClientNum parameter -

So I need a way to test and see if I have passed lClientNum as a parameter - testing for 0 wont work

Please help

Question by:DWE
LVL 26

Expert Comment

ID: 7177008

Accepted Solution

bob_online earned 50 total points
ID: 7177094
IsMissing works in VB6 but not

A better approach, assuming lClientNum is always positive is

Public Sub ShowContact(ID As Long, Optional lClientNum As Long  = -1, Optional bShowButtons As Boolean = False)

If lClientNum >= 0 Then
  do it

End If

The default value for an optional parameter does NOT have to be 0.


Expert Comment

ID: 7177150
Hmm Bob, In you should be overloading the sub (i.e. writing to versions, one with one parameter and one with two) and therefore do not need to use optional parameters

Use ismissing for vb6
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Author Comment

ID: 7177169
Thanks guys

Have a great evening


Expert Comment

ID: 7177171
As bop_online said - use a different value for your default and then test for that value to indicate if the entry is there.

IsMissing will NOT work given your sub declaration, because IsMissing will only work on variant arguments, so you could use:

Public Sub ShowContact(ID As Long, Optional lClientNum As Variant, Optional bShowButtons As Boolean = False)

  If IsMissing(lClientNum) ...

But then you'd have to cast lClientNum to actually use (which may not be a problem), eg:

  If val(lClientNum) = 0 then...

The third (least useful) option is to add another argument which says whether or not to use lClientNum, eg:

Public Sub ShowContact(ID As Long, Optional bUseClientNum as Optional = False, Optional lClientNum As Long, Optional bShowButtons As Boolean = False)

   If bUseClientNum then


Author Comment

ID: 7177177
thanks for the additional information - it is appreciated


Expert Comment

ID: 7177452
You're right, IsMissing only works with variants -- I han't had enough coffee yet this morning...

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