Re: Core Data "Uniqueing" not happening as expected

[Jerry Krinock]

On 2009 Jun 21, at 09:55, Quincey Morris wrote:
Unless you can see 2 different objects with the same UID ...

More precisely, you mean "the same -objectID".

Yup.  To our surprise, my fetch request is returning two objects with  
the same objectID, or from a Core Data perspective, I suppose you'd  
call it two copies of the same managed object.

Here's the fetching code from the NSPersistentDocument subclass in my  
actual project:

NSFetchRequest* fetchRequest = [[NSFetchRequest alloc] init] ;
[fetchRequest setEntity:[NSEntityDescription  
entityForName:@"Browfile_entity"
                                    inManagedObjectContext:[self  
managedObjectContext]]] ;
NSError* error_ = nil ;
NSArray* mocBrowfiles = [[self managedObjectContext]  
executeFetchRequest:fetchRequest
                                                                    
error:&error_] ;
[fetchRequest release] ;
if (error_) {
    // Handle error
    ... this does not execute ...
}
NSLog(
      @"46985: uniqueIDs of fetched objects:\n%@",
      [mocBrowfiles valueForKey:@"stringID"]
      ) ;

NSLog(@"47115: pointers to fetched objects:\n") ;
for (Browfile* browfile in mocBrowfiles) {
    NSLog(@"    %p", browfile) ;
}


Here's my -[NSManagedObject stringID] method:

- (NSString*)stringID {
    NSManagedObjectID* objectID = [self objectID] ;
    NSString* string = [[objectID URIRepresentation] absoluteString] ;
    NSString* suffix = [objectID isTemporaryID] ? @"temp" : @"perm" ;
    return [NSString stringWithFormat:
            @"%...@[%@]",
            string,
            suffix] ;
}


Here's the console output:

2009-06-21 13:04:00.993 TestApp[77117:10b] 46985: uniqueIDs of fetched  
objects:
(
    "x-coredata://101E2F60-412A-41EE-9DEF-59797757C29C/ 
Browfile_entity/p1[perm]",
    "x-coredata://101E2F60-412A-41EE-9DEF-59797757C29C/ 
Browfile_entity/p2[perm]"
)
2009-06-21 13:04:00.995 TestApp[77117:10b] 47115: pointers to fetched  
objects:
2009-06-21 13:04:00.999 TestApp[77117:10b]     0x16e0c9b0
2009-06-21 13:04:01.006 TestApp[77117:10b]     0x16e43f20

I believe that I inserted one Browfile object into the store.  But  
even if I screwed up somewhere and actually inserted two, why does  
this fetch request return two objects with exactly the same permanent  
objectID?  Has anyone ever seen that?

It's not the fact that I'm using an SQLite store.  I tried my little  
utility project with an SQLite store, and saving it, and it works  
correctly.  It still only returns one Bar (aka Browfile).


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