On Oct 24, 2009, at 4:38 PM, Tavis McDevitt wrote:
Don:
As someone who is learning WO I can honeslty say I would have looked
at your tutorials sooner if I'd known about them. They're a great
addition since the best intro material I've seen so far is Apple's
documentation (I've read all of it and it is still really useful and
conceptual), and you help bridge the gap between thier use of
deprecated tools and WOLips. (When I was done with that Chuck's book
became very useful too.)
I've a question though. In your EoModelerBasics show, you made a to-
one relationship from a Person entity to a Cadency entity (a title,
like Jr or Sr).
I learned a new word today. :-)
I get it. You also made the inverse to-many relationship from
Cadency to Person. I don't get that. If I assume that I will never
traverse an inverse relationship (I will never want to know what
people have a Jr in their signature), do I have to model the inverse
relationship? I've been skipping that.
To clarify what Miguel said, I would never model that particular
relationship. If you every need it, you can just fetch them. If you
model this, once you get up to tens or hundreds of thousands of row,
doing an addObjectToBothSidesOfRelationshipWithKey is going to fetch a
LARGE number of rows for no reason.
For things like, er, Cadency, I'd consider NOT modelling it at all. I
think Wonder has some magic to turn codes (e.g. 0, 1, 2 etc.) into
POJO when you fetch.
One more question while I'm at it. What's the best way to model a
linked list? I've thought of putting list items in a table with an
inbred relationship that links to other list items. My concern is
that to retrieve the list at once I'd have to have many trips to the
database, because in a single fault I will only know the root item
in the list, and after each succesive fetch will only have a
reference to one more item. I don't know much about stored
procedures; can one be written to fetch the entire list?
I've used self referencing relationships before, but not for a linked
list. I've only used them when I could fetch all the data at once or
when the relationships only went a few levels. As you point out, more
than that will cause performance problems. If list order is your
concern, then Miguel gave you a good answer. If you are after
something else, we will need more details.
Chuck
Message: 8
Date: Sat, 24 Oct 2009 14:57:11 -0400
From: Don Lindsay <[email protected]>
Subject: Re: 2009 surveys results
To: undisclosed-recipients: ;
Cc: webobjects Apple <[email protected]>
Message-ID: <[email protected]>
Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
I agree with Robert, I created several tutorials for WebObjects as
well as an installer for windows and linux. This is something that I
use my spare time to support.
Based on my review of hits to the tutorials, they are rarely
accessed. If they were used more, I would create more of them.
The tutorials I made are available at:
http://web.me.com/pccdonl/tutorials/WoLipsInstall.htm
as is the installer. (I havent updated the installer in a couple
of months)
Don
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Chuck Hill Senior Consultant / VP Development
Practical WebObjects - for developers who want to increase their
overall knowledge of WebObjects or who are trying to solve specific
problems.
http://www.global-village.net/products/practical_webobjects
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