Solved How to check if an object has been passed to a function?

[KitaYama]

I have this code :

Public Function CreateFilter(Optional frm As Access.Form) As String

    If IsMissing(frm) Then
        Set frm = Screen.ActiveForm
    End If

End Function

When I call the function without any parameter I receive an error on following lines because frm is empty.
How can I check if frm has been passed to the function or not.
IsMissing always returns false, because frm is an object and not a variant.

I've also tried IsEmpty & IsNull. They also always return False.

How can I check if a form has been passed to the function or not?
I can change the data type of frm to string and check if frm="" or not. But for now I prefer to pass a form and not its name.

Thank you.

 

[The_Doc_Man]

There is always the idea that you would pass Me.Name to the function and inside the function would be set as

Set frm = Forms( passed-in-name )

If you did that you would be able to test the form name for being a zero-length string since the default value for a string is a ZLS.

However, there is also the idea that you could set a default value for the object, as say...

Public Function CreateFilter( Optional frm as Access.Frm = Nothing ) As String

Then you could perform an IF frm IS NOTHING test to see if a value was passed in.

 

[KitaYama]

@The_Doc_Man Thanks for your help.

As I said, for now I prefer not to go through what you suggested first.

I corrected my code according to your second solution.

As a conclusion, There's no way to check if an object data type is empty or not. Is that so?

Thanks again.

 

[CJ_London]

'empty' and 'missing' relate to variants datatypes, not objects
'nothing' relates to objects

see these links for more information

The Difference Between Empty, Null and Nothing in VBA - ExcelBaby

Empty Indicates that no beginning value has been assigned to a Variant variable. An Empty variable is represented as 0 in a numeric context or a

excelbaby.com

IsMissing function (Visual Basic for Applications)

Office VBA reference topic

learn.microsoft.com

So this should work

Public Function CreateFilter(Optional frm As Variant) As String

    If IsMissing(frm) Then
        Set frm = Screen.ActiveForm
    End If

End Function

 

[KitaYama]

'empty' and 'missing' relate to variants datatypes, not objects
'nothing' relates to objects

Thanks. This answered my question.

 

[gemma-the-husky]

if not frm is nothing should work.

if not frm is nothing Then
        Set frm = Screen.ActiveForm
End If

sorry - it probably should be the other way round in your case.
if frm IS nothing then ....

the usual construct to avoid a run time error is to use the negative version.
so

if not frm is nothing then
   msgbox frm.name ' avoids generating a rte if frm IS nothing.
end if

 

[KitaYama]

if not frm is nothing should work.

if not frm is nothing Then
        Set frm = Screen.ActiveForm
End If

Yes, I changed my code to this.
many Thanks.