[AccessD] Classes In Referenced MDE

Andy,

>There are also "dirty" tricks to make custom classes in MDB/MDE creatable
using New keyword in FE but I'd not recommend using them

And I do recommend using them, having used them myself for years (since I
learned of Classes from my mentor Shamil).

The method involves exporting the classes to a text file.  

1) Click on a module from the database window:
2) Click File / Export (from the menu)
3) A file find dialog will open.  I usually make a CLASS directory inside of
my project directory.  Move to that directory.
4) type in the name of the file to save it as.  Make the file name the same
as the class name that you are exporting.
5) Open the text file with an editor.  Inside you will see the following at
the top of the module:

VERSION 1.0 CLASS
BEGIN
  MultiUse = -1  'True
END
Attribute VB_Name = "dclsMail"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = False
Attribute VB_Exposed = False
Option Compare Database
Option Explicit

6) Replace all of that with the following:

Attribute VB_Name = "dclsMail"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = True
Attribute VB_PredeclaredId = False
Attribute VB_Exposed = True

Notice that I replaced VB_Creatable with a True value and VB_Exposed with a
true value.

7) Leave the rest of the file untouched, modifying only the lines as shown
above.  Save the text file.

8) Back in the database delete the class you just exported.
9) From the database window click Insert / Class module (from the menu)
10) The VBE will open in a new class.  In the text editor click Insert /
File (from the menu)
11) A file find dialog will open.  Navigate to and select the file you just
modified out in the disk.  It will import the class back in to the database
container (library).

The text file will load into the class module.  NOTICE that the properties
that you modified out in the database window are not visible.  If you could
see or manipulate those properties from inside of the editor this whole
export / modify / import rigmarole would not be required.  IIRC you CAN do
that in VB6 (though I am not a VB6 guru).

11) It will ask if you want to save, say yes.

That class will now be referencable and creatable from outside of the
library.

That is it, you are done.  You are now a member of the ELITE programmers
able and willing to use undocumented tricks to do things others only dream
of.  8~0

IIRC you also have to do this if you intend to RETURN a class from a
function, IOW you can't create a function

function CreateMyClass() AS clsMyClass
end function

then you must go through this process for clsMyClass even if you never
intend it to be seen outside of the library.

I use this process myself (I am "Mr. Framework" after all), but ONLY for
classes that need to be exposed to the outside world, simply because not
performing this process makes a class private to the library, i.e. only
referencable from inside of the lib.  You should never expose things that
you do not want anyone seeing outside of the intended scope.  

Shamil does not recommend this method because these properties (and they are
properties of the class) are undocumented IN VBA by MS and thus "subject to
change".  However they are also used in VB6 (where they are directly exposed
IIRC) and so the chance of this process being prevented in the future is
vanishingly small.  It has been usable since A97, well over 15 years, and is
still usable in A2007.  My framework wouldn't function if I did not use this
trick.  Use it without fear.

HOWEVER... if the process ever does fail (and it hasn't in all the time I
have used it) simply say:

IT'S ALL SHAMIL'S FAULT!

;-)

John W. Colby
Colby Consulting
www.ColbyConsulting.com 
-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Shamil
Salakhetdinov
Sent: Wednesday, December 12, 2007 6:28 AM
To: 'Access Developers discussion and problem solving'
Subject: Re: [AccessD] Classes In Referenced MDE

Hello Andy,

This is a feature by design: you cannot have Creatable custom classes in a
library MDB/MDE.

Although you can have PublicNotCreatable custom classes (you can set this
property via custom class's properties window in VBA IDE, default value is
private) in your library MDB/MDE: they will be visible in FE but you can't
use New keyword to create their instances in FE - the hint/"trick" is to use
helper functions to create instances of these classes in library MDB/MDE....

There are also "dirty" tricks to make custom classes in MDB/MDE creatable
using New keyword in FE but I'd not recommend using them and therefore I'd
not write more on them here...

HTH...

--
Shamil
 
-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Andy Lacey
Sent: Wednesday, December 12, 2007 12:49 PM
To: Dba
Subject: [AccessD] Classes In Referenced MDE

Hi all
I've been experimenting with creating a library of standard functions in
anticipation of a new project. Created MDB, imported modules with standard
functions, created MDE from that and then referenced that MDE in my FE. All
fine and dandy.

Then imported into my library a class module. Recreated MDE. This time
though my FE fails to compile because it doesn't like my Dim of a new
instance of the class - unknown user-defined type. Question is am I doing
something wrong or is this a limitation, ie that class modules must reside
in the FE from which they're called. One of you class experts is sure to
know this one.

--
Andy Lacey
http://www.minstersystems.co.uk