Hi, I'm still trying to sort out what is happening to my to-one relationships
during a Save As operation (see Core data: Inverse relationships with
subclasses thread for context if necessary, but this really is a standalone
thread now) - it turns out that the subclasses/subentities questions were a bit
of a red herring and it applies to all to-one relationships with inverse
relationships. I have narrowed it down to the following:
1. Prior to saving I manually go through all the registered objects and make
sure they pass the validateForInsert and validateForUpdate checks. This
confirms that everything is OK before saving.
2. The Save As operation creates a new atomic store, and loads from an empty
temporary file.
3. It then does a migration to the new atomic store. I really don't understand
this process, but somewhere along the way, it calls awakeFromFetch on all my
existing managed objects (even though as far as I can tell, no fetches have
been done, and certainly no new atomic store cache nodes have been created).
4. It then validates my managed objects, and this time the insert validation
checks fail for all my to-one relationships that have inverse relationships.
Here is a typical failure (they happen on validateForInsert:):
Error Domain=NSCocoaErrorDomain Code=1550 UserInfo=0x11baadf10 "backgroundStyle
is not valid."
{
"Dangling reference to an invalid object." = "<null>";
NSAffectedObjectsErrorKey = (
"<NMFillStyleMO: 0x11b75b290> (entity: FillStyle; id: 0x11b7a8090
<x-coredata://7FFCE521-A755-4341-86DE-971B085D77D7/FillStyle/tB496F77D-2950-43FF-93CC-B49FEE7FF269207>
; data: {\n ... theme = \"0x11b7a8f80
<x-coredata://7FFCE521-A755-4341-86DE-971B085D77D7/Theme/tB496F77D-2950-43FF-93CC-B49FEE7FF269226>\";\n
... })"
);
NSLocalizedDescription = "backgroundStyle is not valid.";
NSValidationErrorKey = backgroundStyle;
NSValidationErrorObject = "<NMThemeMO: 0x11b75eb50> (entity: Theme; id:
0x11b7a8f80
<x-coredata://7FFCE521-A755-4341-86DE-971B085D77D7/Theme/tB496F77D-2950-43FF-93CC-B49FEE7FF269226>
; data: {\n ... backgroundStyle = \"0x11b7a8090
<x-coredata://7FFCE521-A755-4341-86DE-971B085D77D7/FillStyle/tB496F77D-2950-43FF-93CC-B49FEE7FF269207>\";\n
... })";
NSValidationErrorValue = "<NMFillStyleMO: 0x11b75b290> (entity: FillStyle;
id: 0x11b7a8090
<x-coredata://7FFCE521-A755-4341-86DE-971B085D77D7/FillStyle/tB496F77D-2950-43FF-93CC-B49FEE7FF269207>
; data: {\n ... theme = \"0x11b7a8f80
<x-coredata://7FFCE521-A755-4341-86DE-971B085D77D7/Theme/tB496F77D-2950-43FF-93CC-B49FEE7FF269226>\";\n
})";
}
Now seeing as my code has not touched the managed objects since I last
validated them, all I can assume is that either:
a) I have something set up incorrectly in my model which is causing the
problems (I can't see how, but I guess it's possible)
b) I have not set things up correctly in the cache nodes, and it's trying to
populate the managed objects with something invalid (I don't see how this could
be the case, seeing as the ordinary loading and saving works fine)
c) I have set up something incorrectly in the managed objects which is causing
these relationships to not be established properly upon migration of the store
(again, I can't see how), or
d) something I haven't thought of or am not aware of...
When I break on the validation, the objects all exist, they are valid, the
relationships exist, and I can use valueForKey to traverse the relationships in
both directions. As you can see from the above, the theme object has a
reference to the background style which is a fill style, and indeed the fill
style exists and the address matches, and the fill style has a "theme"
relationship that points back to the theme object.
I can't help thinking that if I understood what is going on behind the scenes
during Save As, I might be able to have a chance of working this out.
I'd really appreciate it if someone could give me a clue as to what may be
causing this.
Thanks
Gideon
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