Re: EO: Should I create primary keys?
Re: EO: Should I create primary keys?
- Subject: Re: EO: Should I create primary keys?
- From: Arturo Pérez <email@hidden>
- Date: Mon, 28 Jul 2003 06:57:36 -0400
On Monday, July 28, 2003, at 05:46 AM, Goodbye Bill wrote:
HEEELP! SQL is pulling me back in! M-m-m-ust... n-n-not... go...
back!
QUESTION:
Should I create assign/create my primary keys myself OR should I [is it
possible to] rely entirely upon EO to do it?
You can rely on EO to do it, except for a few funky cases. But even in
those
cases there is an EO mechanism to do it.
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.
The above makes it sound as though you are programmatically creating
tables
and relationships. If you're using EOModeller then I can't see how to
avoid
the above.
The typical scenario is, assuming a completely empty schema.
Make Entity A. That usually means making a table and defining its
columns.
The columns are usually Entity A's attributes. I don't think you need
to
worry about foreign keys. You do have to designate which attribute is
the
primary key by turning on the key icon.
Make Entity B. Add its attributes.
Add a relationship between the two. You can either do it by
control-dragging
from one attribute in A to an attribute in B OR by hitting the add
relationship
button and filling in the resultant dialog box. Call this relationship
"toAfromB".
Then, in your code, when you want to make the relationship in your code
you do
addObjectToBothSidesOfRelationshipWithKey(BObjectInstance, "toAfromB")
and you're done.
-------
WebObjects in Philadelphia. You want a cheesesteak with that?
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