Whats the equivalent of null in VBA?

[Guest]

Hi,
I have the following code:
Public parent As Node
Set parent = New Node
parent = Null

This doesnt work (Error 438). The error is on the last line, where I try to
assign a null value to parent. How do I assign null values to objects in VBA?

Btw, "Node" is defined as a class module.

Thanks.

 

[Guest]

try

parent = vbNullString

 

[Guest]

You might want to use something other than parent - might be reserved.
anyway try:
set parent=Nothing

 

[Guest]

hi,
try parent = ""

regards
FSt1

 

[JE McGimpsey]

First, take a look at Null in VBA Help.

To dissociate object variables from their objects, you set them to
Nothing:

Set parent = Nothing


For most simple cases, that's not really necessary since the object will
be destroyed when the object variable goes out of scope (i.e., when the
Sub exits).

 

[Tim]

Set parent = Nothing

Tim

 

[Guest]

I'll try all of these work arounds. I'll only be able to test if they work
when my application is 'semi-complete'.

Why are all of these work arounds? Is there no such 'null' as there is in
other languages?

 

[moon]

You might want to use something other than parent - might be reserved.
anyway try:
set parent=Nothing

And 'Node' is reserved as well.

 

[Guest]

This is the VBA explanation for the term NullString:

Returns or sets the string displayed in cells that contain null values when
the DisplayNullString property is True. The default value is an empty string
(""). Read/write String.

 

[JE McGimpsey]

However, Null is different than the null string (look up Null in VBA
Help)

 

[Tim]

Set someObject = Nothing

is a perfectly normal thing to do *in VBA*: it's not a "workaround".

I suspect that some of the other suggestions you got were from mis-reading
your original question.

Tim

 

[Guest]

They're not really workarounds - just not positive what you are trying to
accomplish. It looks to me like the suggestions using "", vbnullstring, etc
were prompted by you not using a set statement in the example provided (which
is required for objects). It looks like you could be trying to assign null
to a default property of the parent object or you could be trying to destroy
the parent object itself (ie-set it to nothing).

 

[NickHK]

It seems that your idea that "work arounds" are required stems from your
misunderstanding the VBA/VB language and what Null means.
To me, outside of a database environment, it does not have a real meaning in
VBA, where you have Nothing for objects and Empty for variants (although you
can use Null with a Variant also) & vbNullString for strings.

Private Sub CommandButton1_Click()
Dim Nullable As Variant

Nullable = "some string"
Nullable = Null
Debug.Print IsNull(Nullable)

Nullable = "some string"
Nullable = Empty
Debug.Print IsNull(Nullable)

Dim NullStr As String
NullStr = "Null String"
NullStr = vbNullString
Debug.Print IsNull(NullStr)

End Sub

NickHK