[AccessD] RE: Instantiate Forms as Objects

David,

Intriguing ... assigning the responsibility of creating the form instance to
the form class itself.

I have several comments regarding your code:

1. If you copied "TestForm" to "New_Form", New_Form.NewInstance would create
TestForm instances, an implicit mismatch. To catch this error, I would
suggest:
    Public Function NewInstance() As Access.Form
        If Not (TypeOf Me Is Form_TestForm) Then
            ' Raise Type Mismatch Error
            Err.Raise 13, "Form_" & Me.Name & ".NewInstance", "Type
mismatch"
        End If
        Set NewInstance = New Form_TestForm
    End Function

This way, TestForm.NewInstance works, but New_Form.NewInstance generates a
runtime error, prompting you to fix the routine.

2. To avoid the screen flicker, you could try opening the form with acHidden

3. Regarding the problem you mentioned, I would suggest putting all form
references into a collection. You could key it with the Form.Hwnd property,
as MarkH did in his code. Closing a form would be a matter of setting focus
to the form, issuing a DoCmd.Close, and removing it from the collection.

This approach is as workable as any other. The nice thing about it is, if
you delete a form, you don't have to update your form creation function. If
you copy a form, you still have to remember to modify its NewInstance
function, which is not a bad tradeoff.

-Ken

-----Original Message-----
From: David Beckles [mailto:becklesd at tiscali.co.uk]
Sent: Wednesday, January 21, 2004 7:11 PM
To: accessd at databaseadvisors.com
Subject: [AccessD] RE: Instantiate Forms as Objects


Dear Ken,
One way of achieving (most of) what you want to do is as follows:

1. In each of your forms create the function
Public Function NewInstance() As Form
     Set NewInstance = New Form_TestForm
End Function

Its purpose is merely to return a reference to a new instance of the form.
You could also define it as a new public property of the form, instead of a
function.

2. Define the following function in some general module

Public Function OpenFormMultiple(FormName As String) As Form
     ' check the Forms collection, and if the form is in it then use the
NewInstance() method of the form
     ' otherwise open the form in the usual way and return a reference to
it.
     ' in either case, the form will not be visible.
     ' if any errors occur, then the value Nothing will be returned, so
remember to test for it.

     On Error Resume Next        ' You could use fancier error handling if
you wanted
     Dim F As Form

     Set OpenFormMultiple = Nothing
     Set F = Forms(FormName)
     If F Is Nothing Then
         Application.Echo False  ' this is to suppress the screen flicker
         DoCmd.OpenForm FormName
         Set F = Forms(FormName)
         F.Visible = False
         Set OpenFormMultiple = F
         Application.Echo True
     Else
         Set OpenFormMultiple = F.NewInstance()
     End If
End Function

One problem with this arrangement is that you can close all the instances
of a form except the first by setting the reference to Nothing. The first
instance has to be closed by going into the Forms collection. I have not
found a way around that as yet.

I hope that this helps,
David