Properties for a custom class (not a collection)

[downwitch]

Hi,

I know this has been covered here and in the .public groups, but it
seems like it's been a while, especially around here, so I just thought
I'd ask again to see if anyone has figured out a new angle.

If I have a class MyClass--not a collection container but a
single-level class--that has a bunch of properties of different types,
I'd like to be able to reference them via the standard VBA syntax of

MyClass.Propert ies("MyProperty ")

or

MyClass.Item("M yProperty")

so that I could use variables instead of having to say

MyClass.MyPrope rty

to get and let.

Of course, I could create a whole collection myself to loop using the
Item/IEnumerator trick, but seems to me that kind of squashes the
usefulness of properties in the first place.

Thanks in advance.

[lylefair]

Since Access 2000 one can put properties into a Standard Module.
One can reference them as ModuleName.Prop ertyName

example (in a standard module called PseudoClass)

Dim mInput As Double

Public Property Let InputNumber(ByV al vInput As Double)
mInput = vInput
End Property

Public Property Get TwelfthRoot() As Double
TwelfthRoot = mInput ^ (1 / 12)
End Property

---------------------
somewhere else

PseudoClass.Inp utNumber = 29
MsgBox PseudoClass.Twe lfthRoot
'Shows
'---------------------------
'Microsoft Office Access
'---------------------------
'1.323934501112 41
'---------------------------
'OK
'---------------------------

That being said, one of the great values of Classes is that multiple
instances can be created. TTBOMK only one instance of a Standard module
can exist at one time.

As well, these properties seem to operate no differently than Subs and
Functions, (well maybe a bit slower).

[downwitch]

Thanks, but that's not what I'm asking. To use your example, I want to
be able to do this.

MsgBox PseudoClass.Pro perties("Twelft hRoot")

So that I could potentially say

Dim strTest as string
strTest="Thirte enthRoot"
MsgBox PseudoClass.Pro perties(strTest )

That's a silly example, but if for example you want to return a bunch
of different properties with a single piece of code, you begin to see
how Class.Property is a limitation.

[David Lloyd]

The following MSDN article shows how to make the Item property the default
property of a collection. It requires using Procedure Attributes, normally
set in Visual Studio 6.

http://msdn.microsoft.com/library/de...seofbricks.asp

--
David Lloyd
MCSD .NET
http://LemingtonConsulting.com

This response is supplied "as is" without any representations or warranties.
"downwitch" <do*******@gmai l.com> wrote in message
news:11******** *************@g 49g2000cwa.goog legroups.com...
Hi,

I know this has been covered here and in the .public groups, but it
seems like it's been a while, especially around here, so I just thought
I'd ask again to see if anyone has figured out a new angle.

If I have a class MyClass--not a collection container but a
single-level class--that has a bunch of properties of different types,
I'd like to be able to reference them via the standard VBA syntax of

MyClass.Propert ies("MyProperty ")

or

MyClass.Item("M yProperty")

so that I could use variables instead of having to say

MyClass.MyPrope rty

to get and let.

Of course, I could create a whole collection myself to loop using the
Item/IEnumerator trick, but seems to me that kind of squashes the
usefulness of properties in the first place.

Thanks in advance.

[Bri]

lylefair wrote:

Since Access 2000 one can put properties into a Standard Module.
One can reference them as ModuleName.Prop ertyName

I was curious, so I have verified that this works in AC97 as well.

--
Bri

[downwitch]

While I appreciate the attempts to help, please take a moment to read
the subject line and the first post before so doing.

I am intimately familiar with constructing classes and collections. I
am trying to find a workaround to the fact that VBA will let you build,
set, let, get, etc. a property, but does not expose the properties as a
native collection through which one can loop as one does through any
other native collection, such as a form's properties, or yes, as one
does through a collection object. I don't hold out much hope, but I
figured it was worth dashing the little bit I had for good, and this
would be the place to do it.

[lylefair]

I misread your post. Me Bad. Sorry!

[downwitch]

Not a problem. All in a day's work!

lylefair wrote:

I misread your post. Me Bad. Sorry!

[David W. Fenton]

"downwitch" <do*******@gmai l.com> wrote in
news:11******** **************@ g44g2000cwa.goo glegroups.com:

That's a silly example, but if for example you want to return a
bunch of different properties with a single piece of code, you
begin to see how Class.Property is a limitation.

What you're asking for is a collection that you can walk to get the
properties.

There is no way to do this in Access class modules. THe only way to
implement it is either with a custom collection or an array stored
in class module, with an interface for allowing you to enumerate its
values. I don't believe an array can be a public member, but you
should be able to create a public property of type array.

I've only wanted to walk the properties collection of a class module
internally, never externally, so I've only implemented it with an
array.

But once you're at that point, you have to ask yourself:

1. will you allocate a variable for each property, then double enter
it into an array?

OR

2. will you use the array for storing all the properties, and then
have the property LET/GETs operate directly on the array, and
completely ignore internal variables.

I don't know if the latter slows things down.

The former is easy enough, and that was how I implemented it, but I
was adding functionality to a class that was already in list, so I
needed backward compatibility.

--
David W. Fenton http://www.bway.net/~dfenton
dfenton at bway dot net http://www.bway.net/~dfassoc

[David W. Fenton]

"downwitch" <do*******@gmai l.com> wrote in
news:11******** *************@o 13g2000cwo.goog legroups.com:

I am intimately familiar with constructing classes and
collections. I am trying to find a workaround to the fact that
VBA will let you build, set, let, get, etc. a property, but does
not expose the properties as a native collection through which one
can loop as one does through any other native collection, such as
a form's properties, or yes, as one does through a collection
object. I don't hold out much hope, but I figured it was worth
dashing the little bit I had for good, and this would be the place
to do it.

I posted in response to Lyle and explained one approach I've used.

It involves creating either your own internal custom collection or
an array to store the properties, then exposing that externally in
some fashion.

Having done it before, I immediately grasped the question -- you
want to be able to walk the properties collection of your class.

I use a class for storing the criteria for query-by-form interfaces,
and when writing the SQL, being able to walk a collection in order
to write the WHERE string would have been highly desirable. I
implemented an internal array, so I avoided the problems associated
with making the contents of an array in a class module public.

--
David W. Fenton http://www.bway.net/~dfenton
dfenton at bway dot net http://www.bway.net/~dfassoc