Re: Empty relationship that isn't null
Re: Empty relationship that isn't null
- Subject: Re: Empty relationship that isn't null
- From: DevReseune <email@hidden>
- Date: Sun, 22 May 2005 18:31:11 +0200
Hi,
Thanks for your response, but my problem is still there.
I resume with more details:
#1
I have 2 entities:
- PARENT:
- PK: String ID
- to-one relationship: CHILD child with:
- PARENT.ID = CHILD.PARENTID
- optionnal
- delete rule: nullify
- owns destination: no
- propagate primary key: no
- CHILD
- PK: String PARENTID
NOTE: PARENT is related with another entity, and the primary key of
PARENT is the primary key of this other entity.
#2
In database, I have only 2 PARENTs, and 0 CHILD.
#3
First, I fetch all PARENTs:
- EOF calls a SQL request to load all PARENT
- the attribute PARENT.child is initiated with a
EOAccessDeferredFaultHandler object
> update with takeStoredValueForKey
#4
So, in another page, I show an PARENT:
- EOF calls a SQL request to load a related CHILD with PARENT
> the response is "0 row(s) proceed". It's true, no CHILD exists in
database
- he attribute PARENT.child is setted with a _EOVectorKeyGlobalID
object with all its properties are
> update with takeStoredValueForKey
Any suggestion?
Frédéric
Le 18 mai 05 à 22:23, Ken Anderson a écrit :
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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