Re: Non Compulsory toOne Relationships, Propergating Primary Key
Re: Non Compulsory toOne Relationships, Propergating Primary Key
- Subject: Re: Non Compulsory toOne Relationships, Propergating Primary Key
- From: Chuck Hill <email@hidden>
- Date: Fri, 7 Dec 2007 10:51:15 -0800
On Dec 6, 2007, at 11:50 PM, Art Isbell wrote:
On Dec 6, 2007, at 8:18 PM, Owen McKerrow wrote:
I have the following relationship :
GROUP <-- --> RQF_GROUP
where a group may have a RQF Group object, but the RQF Group
object must belong to a group.
As its a to one I want it to propagate its primary key across,
however when I tick this box WO is nice and helpful and inserts a
new RQFGroup object every-time I make a new Group, even thought I
have specified that the relationship is optional. Is there any way
to stop this from happening ?
If I understand correctly, you want the primary key of the
RQF_GROUP object to be the same as that of GROUP object. If so,
you can't have an optional to-one relationship in which the foreign
key of the GROUP.RQF_GROUP relationship is non-null. The foreign
key of this relationship can't be null because it's the GROUP
object primary key. So WO graciously creates an RQF_GROUP object
for you which isn't what you want.
This situation is described in "Tips for Specifying Relationships"
in the EOModeler User Guide at <http://developer.apple.com/
documentation/WebObjects/UsingEOModeler/5WorkingWithRelationships/
chapter_5_section_4.html>:
A to-one relationship from one foreign key to a primary key
Typo: should read "from a primary key to a primary key"
must always have exactly one row in the destination entity—if this
isn’t guaranteed to be the case, use a to-many relationship. This
rule doesn’t apply to a foreign key to primary key relationship
where a null value for the foreign key in the source row indicates
that no row exists in the destination.
Aloha,
Art
--
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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