Re: Empty relationship that isn't null
Re: Empty relationship that isn't null
- Subject: Re: Empty relationship that isn't null
- From: Ken Anderson <email@hidden>
- Date: Wed, 18 May 2005 16:23:15 -0400
To expand a little bit on what Chuck is saying, if a value exists in
a column being used to construct a relationship, EOF believes that
the related object exists. If you use the same primary key for
related EO's (for instance, a primary EO, and an optional 'sidecar'
object), you can run into this problem, since the primary key of the
primary EO always exists, it is expected that the related object
always exists.
This occurs often in databases that were designed without EOF in
mind. A typical way to work around this is to make the relationship
to-many, then have a custom accessor in the EO of the single variety
that either returns toMany.firstObject() or nil, depending on whether
there's a count on the relationship or not.
Ken
On May 18, 2005, at 4:12 PM, Chuck Hill wrote:
We are talking about a specific object that is related to a
specific row in the database. Does that row have a non-null value
for the EntityB FK? If so, is it valid or do you have a
referential integrity problem in your data? If you have a
referential integrity problem (which is what it sounds like), then
you are seeing what is called a "Dummy Fault EO" see http://
lists.apple.com/archives/webobjects-dev/2003/Aug/msg00433.html and
other Google hits.
Chuck
On May 18, 2005, at 12:46 PM, DevReseune wrote:
Hi,
It's an optional to-one relationship, there is none EntityB in
database, and the entityB FK is null by default, but this property
is hidden (not the related object, but its ID).
I don't understand.
Frédéric
Le 16 mai 05 à 21:24, Chuck Hill a écrit :
This is a to-one relationship? Is it marked as optional or
mandatory? Is the entityB FK in the EntityA object null, or does
it have a value?
Chuck
On May 16, 2005, at 11:19 AM, DevReseune wrote:
Hi,
I have 2 entities bound with a relationship:
- EntityA
- entityB -> EntityB
- EntityB
When I fetch an EntityA, the relationship entityB is initialited
with an EOAccessDeferredFaultHandler (takeStoredValueForKey)
while the SQL select statement returns 0 row.
When I try to access to the relationship entityB, it is updated
with an _EOVectorKeyGlobalID (takeStoredValueForKey).
But, I expected a null value. What's the problem?
Webobjects 5.2.4
MacOS X Tiger (I have the same behavior on X.3).
Frédéric _______________________________________________
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developers who want to increase their overall knowledge of
WebObjects, or those who are trying to solve specific application
development problems.
http://www.global-village.net/products/practical_webobjects
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