Re: EO: Creating Relationships - BOGUS?
Re: EO: Creating Relationships - BOGUS?
- Subject: Re: EO: Creating Relationships - BOGUS?
- From: Art Isbell <email@hidden>
- Date: Fri, 1 Aug 2003 16:55:16 -1000
On Friday, August 1, 2003, at 04:13 PM, Goodbye Bill wrote:
How the heck is one supposed to create ONE-to-many relationships?
There's an "New Relationship in Selected Entity" button in the toolbar
along the top of the EOModeler window or a Property > Add Relationship
menu.
Now, I WOULD LIKE to be able to create my objects as BASIC as possible
(with
only my properties)... WITHOUT me having to specify ANY keys. THEN,
click a
button or three and have EO take care of the rest, behind the scenes.
Now you're getting the picture :-)
Example:
ENTITY #1 : "Album"
PROPERTIES: "Name" (notice there is only one)
ENTITY #2 : "Song"
PROPERTIES: "Name" (notice there is only one... again)
Using the example above, I want to be able to add a one-to-one
relationship
to the "Album" entity (probably called "Songs") and have EO create all
of
the primary and foreign key relationships.
To your model, you'll have to add Album.oid and Song.oid primary keys
and a Song.oidAlbum foreign key, none of which are class properties and
so won't be referenced in your code. But they will be a real DB
columns. You'll join Song.oidAlbum to Album.oid in the Relationship
Inspector when you create the Song.album relationship. You'll do the
same creating the inverse relationship, Album.songs. This can be done
in a single step using in the Diagram view by control-dragging a
relationship from Song.oidAlbum to Album.oid, for example.
At this point I usually try to decide whether I'm really going to
traverse the object graph in both directions (i.e., using both
Song.album and Album.songs). I try not to, so I make only one of these
relationships a class property to avoid fetching that's not necessary
if I'm not traversing the object graph in both directions.
Aloha,
Art
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