Re: EO: Should I create primary keys?
Re: EO: Should I create primary keys?
- Subject: Re: EO: Should I create primary keys?
- From: Denis Stanton <email@hidden>
- Date: Tue, 29 Jul 2003 11:40:27 +1200
I believe Bills problem here is he hasn't seen the place to define
relationships is in EOModeler so he's trying to do all the work himself.
Bill (or may I call you Goodbye? :-) ), you set up the relationships
inside EOModeler with just a few clicks and then it does all the
primary key / foreign key stuff for you. That's why the keys are not
class properties - you don't (normally) have to do anything with them.
Have another look at EOM. One of those circular icons along the top
adds relationships.
Denis
On Tuesday, July 29, 2003, at 04:56 AM, Jonathan Rochkind wrote:
PROBLEM:
To create any relationship, one must specify the source and
destination
properties (essentially, the primary and foreign keys within the
table).
This means that the developer is forced to create the columns for the
keys,
assign the key attribute, etc., both while creating the table and
while
creating the relationship. This seems to violate the initial goal of
EO,
which is to extrapolate the database and the object model.
I'm not following you. Why is this a problem? Yes, to create a
relationship in an EOModel, the developer must specify what columns
are used for fk/pk, and then use these columns in the relationship
definition. That's how you tell EOF how the relationship is defined,
true. Once you've done that, you can generally ignore those columns.
They shouldn't ordinarily be class properties. In your Java code, you
can (and generally should) deal only with the relationship, not with
the columns.
I don't see why this is a problem, but, yes, this is the way EOF
works. Sure, EOF makes the db and the object model somewhat
independent. But they still need to be tied together _somewhere_. The
EOModel is the place they are tied together---the point of the EOModel
is basicaly to explain how the object model relates to the db. So of
course you need to refer to db columns in the EOModel.
Denis Stanton
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