Look for design solution to transfer data from business object to a dialog box object

Look for design solution to transfer data from business object to a dialog box object

Post by Christophe Addinqu » Mon, 06 Apr 1998 05:00:00



I'm looking for design solutions to transfer data from application object
to dialog box object.
My need is to respect the object oriented goals. Mainly, object's internal
data must remain hidden. So, I reject solutions using access methods to
load data from the business object to the dialog box and reverse.
The scope of this problem is not restricted to communication between
business object and dialog boxes. It may be extended to communication
between business object and another object localized in a peripheral
subsystem, and representing the first one. But on the other hand, the
problem doesn't deal with distributed objects.
If anybody was faced with the same problem, I wish to know what solution or
design pattern he chooses. If you outlined this problem dusring design
time, but don't saw any good solution, I'm interested too.

--
Christophe Addinquy, Paris - France

--- Object IS the essential ---

 
 
 

Look for design solution to transfer data from business object to a dialog box object

Post by Patrick Loga » Tue, 07 Apr 1998 04:00:00


: I'm looking for design solutions to transfer data from application object
: to dialog box object.
: My need is to respect the object oriented goals. Mainly, object's internal
: data must remain hidden. So, I reject solutions using access methods to
: load data from the business object to the dialog box and reverse.

A good paper to read would be one by Wirfs-Brock in the Communications of
the ACM from the OO issue several years ago. I think it may have been in
1992, but a search would provide the information. The paper is about
"Responsibility-Driven Design". The point is that if the user has to
interact with the system based on some information already in the system,
then it makes sense for something in the user interface to be able to get
the information from the model one way or another.

What are your concerns about providing access to the information the user
interface requires? If you do not want to reveal the structure of the
information then you can look at, say, the Visitor pattern from the Design
Patterns book, Gamma, et al. If you do not want the clients to alter the
information then you can provide access to copies or to read-only
interfaces to the information.

--


                 http://www.gemstone.com

 
 
 

1. distributed business objects and granularity design

Hello,

  We recently purchased an application server (java ejb based), and as
part of the product they sent us a prototype - example application.
Part of the application was a domain partitioning framework that I
find both interesting and perplexing at the same time.  I'd like to
hear what you guys think about their approach, and my thoughts on
their approach.

They essentially build their domain objects with the following concer
seperation.

DomainObject    DomainIdentity  DomainState

The identity is just the displayable name of the object (for filling
in select lists, et), the state is the bare bones of the object (used
for distribution), and the object is a completely reified domain
object.  The domain object and state keep a pointer to the  identity,
and the object keeps a pointer to the state.

Asci art sucks in a relative font so I bear with me

DomainObject  ---->  DomainState  ------>  DomainIdentity
          |                                                      ^
          |-------------------------------------------------------|

Hopefully that somewhat conveys the picture.  

Here's my take on it.  While a very useful seperation, it isn't OO.

A DomainObject ISA DomainState which ISA DomainIdentity.  In c++ you
could use MI and still get nice clean seperation, and good inheritance
based abstraction.  In java you're screwed.  And should do this

DomainIdentity
     ^
     |
     |
DomainState
    ^
    |
    |
DomainObject    

Which means that each cannot have its own base class for shared
functionality -- which is pretty lame.   But at least you do get
functional polymorphism.  Its an interesting quandary -- at least to
me.  Has anyone come up with other neat ways to seperate object
"reified -ness" (a new word?) for distribution overhead reduction.    

If this has already been beaten to death on this forum, I apologize, I
don't read (or post) much anymore.

Thanks
Brad


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