Question regarding oo design / layers

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

Rob Meade - 21 Jun 2007 16:41 GMT

Hi all,

Ok - I have a few objects I've created, some live in my dal, some in my bol
and some in my ui...

Here's the thing - I have the need to persist an ID which is used for
display purposes only (control ID) and the only place I can persist this is
in one of my objects (session variables are not acceptable)....the problem
is - the object which it would most likely go in belongs in my bol...to me
this feels wrong, oh so very wrong, as my understanding, whilst limited is
that objects in my bol should not know about ui things equally not know
about dal things...

So, here's the question - would it be more appropriate to have a UI object
specifically created and form part of my bol object as opposed to just
having a class variables in bol object?

Example...

bol object

Resource object

private _displayControlID as guid

OR

Control object

private _controlID as guid

and then have

Resource Object

Private _controlObject as ControlObject

Does the above make any sense? Hope so - not easy to explain and didn't want
to write mammoth amounts of code to explain it...any advice would be
appreciated..

Regards

Rob

Reply to this Message

Peter Bradley - 21 Jun 2007 16:57 GMT

I don't know if this is any help, but we usually create UI objects that hold
the sort of thing that you're talking about, if I understand you correctly.
We store references to them in the Session. The data in these objects
reflects their state resulting from user input or other UI-specific things
(like default display values and so on). This data is validated as
appropriate, and has the appropriate business rules applied each time the
user leaves a page (or saves the data). It is at this point that the data
is passed from the UI layer to the business layer: and obviously we only
pass the data that we need at the BOL and DAL levels.

HTH

Peter

> Hi all,
>
[quoted text clipped - 40 lines]
>
> Rob

Reply to this Message

Rob Meade - 22 Jun 2007 14:37 GMT

>I don't know if this is any help, but we usually create UI objects that
>hold the sort of thing that you're talking about, if I understand you
[quoted text clipped - 5 lines]
>is passed from the UI layer to the business layer: and obviously we only
>pass the data that we need at the BOL and DAL levels.

Hello Peter,

Thank you for your reply.

That makes sense to me I think, and I think it will fit with my current
project - just to run it past you in more depth...

I have a registration process with three stages, the third stage the user
selects "resources" which they require access to, this is done via a link on
the page which launches a popup window listing all available resources.
When the user selects one a little bit of a javascript populates a hidden
element on the parent page and fires a Click() event on a hidden button on
the parent page. Ajax then enables me to perform an asynchronous postback -
and this is where the magic happens!

I populate a "Resource" object, and using the ResourceID get the available
Access Levels for it.

The ResourceName is displayed on the page, underneath a drop down list
containing all of the AccessLevels, a second drop down box is also
displayed, this is populated again using Ajax when the user selects an
AccessLevel.

Because the user can add as many Resources as they wish the page builds up
with these controls, the problem I have run into is that I need the ability
to give it collection of bits a unique ID - and persist it. I am unable to
use the ResourceID as they can select the same resource more than once (by
design), therefore I want to create a GUID but store it.

If I was to create a UI object, and part of that object stores the GUID and
another part stores my Resource, AccessLevel choice, Parameter (second drop
down) choice - would this still *fit* the OO / Layers rules?

A screenshot of the page in question can be seen here:
<http://www.avon.nhs.uk/RobsToGo/ScreenShot.jpg>

Any further information would be appreciated.

Regards

Rob

Reply to this Message

Question regarding oo design / layers

Free Magazines