Re: NSManagedObjectContext -insertObject: Cancels Prior Deletion -- BUT!

[Jerry Krinock]

Thanks for the answers, "yes" and "no", but I've found a problem doing  
so....

1.  Insert a managed object.
2.  Set an attribute in the object.
3.  Delete the object from its moc.
4.  Execute a fetch request in the moc with no predicate.
5.  Get the attribute from the object.
Expected Result: The attribute set in step 2
  Actual Result: nil

Why does the attribute disappear?  Continuing, the attribute does not  
come back after re-inserting the object.  Also, I've tried a - 
processPendingChanges before deleting, but that does not help.

Here are the steps written in code:

// Insert a Foo and name it "Murphy"
NSManagedObject* foo = [NSEntityDescription  
insertNewObjectForEntityForName:@"Foo"
                                                      
inManagedObjectContext:moc] ;
[foo setValue:@"Murphy"
       forKey:@"name"] ;

// Delete the Foo from the moc
[moc deleteObject:foo] ;

// Create a fetch request for all objects.
NSFetchRequest* fetchRequest = [[NSFetchRequest alloc] init];
[fetchRequest setEntity:[NSEntityDescription entityForName:@"Foo"
                                    inManagedObjectContext:moc]];

// Execute the fetch request
// (Note: We ignore the fetch result.)
NSLog(@"1000 name of foo: %@", [foo valueForKey:@"name"]) ;
[moc executeFetchRequest:fetchRequest
                   error:NULL] ;
NSLog(@"2000 name of foo: %@", [foo valueForKey:@"name"]) ;

// Re-insert the Foo into the moc
[moc insertObject:foo] ;
NSLog(@"3000 name of foo: %@", [foo valueForKey:@"name"]) ;


Console Output:

2009-05-05 14:25:43.533 CoreDataUtility[8186:10b] 1000 name of foo:  
Murphy
2009-05-05 14:25:43.537 CoreDataUtility[8186:10b] 2000 name of foo:  
(null)
2009-05-05 14:25:43.539 CoreDataUtility[8186:10b] 3000 name of foo:  
(null)



In case anyone would like to run the code, here's the whole project in  
one file.  It's based on Apple's Core Data Utility Sample Project:

#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>

// Note: This method returns a retained, not autoreleased, instance.
NSManagedObjectModel *getStaticManagedObjectModel() {
    static NSManagedObjectModel *mom = nil;

    if (mom != nil) {
        return mom;
    }

    mom = [[NSManagedObjectModel alloc] init];

    NSEntityDescription *fooEntity = [[NSEntityDescription alloc]  
init];
    [fooEntity setName:@"Foo"];
    [fooEntity setManagedObjectClassName:@"Foo"];
    [mom setEntities:[NSArray arrayWithObject:fooEntity]];

    NSAttributeDescription *nameAttribute;

    nameAttribute = [[NSAttributeDescription alloc] init];
    [nameAttribute setName:@"name"];
    [nameAttribute setAttributeType:NSStringAttributeType];
    [nameAttribute setOptional:YES];

    [fooEntity setProperties:[NSArray arrayWithObject: nameAttribute]];

    [fooEntity release] ;

    return mom;
}

// Note: This method returns a retained, not autoreleased, instance.
NSManagedObjectContext *getStaticManagedObjectContext() {

    static NSManagedObjectContext *moc = nil;

    if (moc != nil) {
        return moc;
    }

    moc = [[NSManagedObjectContext alloc] init];

    NSPersistentStoreCoordinator *coordinator =
    [[NSPersistentStoreCoordinator alloc]
     initWithManagedObjectModel: getStaticManagedObjectModel()];
    [moc setPersistentStoreCoordinator: coordinator];
    [coordinator release] ;

    NSError *error;
    NSPersistentStore *newStore ;
    newStore = [coordinator  
addPersistentStoreWithType:NSInMemoryStoreType
                                         configuration:nil
                                                   URL:nil
                                               options:nil
                                                 error:&error];

    if (newStore == nil) {
        NSLog(@"Store Configuration Failure\n%@",
              ([error localizedDescription] != nil) ?
              [error localizedDescription] : @"Unknown Error");
    }
    return moc;
}


int main (int argc, const char * argv[])
{
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    // Create Core Data stack
    NSManagedObjectModel *mom = getStaticManagedObjectModel();
    NSManagedObjectContext *moc = getStaticManagedObjectContext();

    // Insert a Foo and name it "Murphy"
    NSManagedObject* foo = [NSEntityDescription  
insertNewObjectForEntityForName:@"Foo"
                                                          
inManagedObjectContext:moc] ;
    [foo setValue:@"Murphy"
           forKey:@"name"] ;

    // Delete the Foo from the moc
    [moc deleteObject:foo] ;

    // Create a fetch request for all objects.
    NSFetchRequest* fetchRequest = [[NSFetchRequest alloc] init];
    [fetchRequest setEntity:[NSEntityDescription entityForName:@"Foo"
                                        inManagedObjectContext:moc]];

    // Execute the fetch request
    // (Note: We ignore the fetch result.)
    NSLog(@"1000 name of foo: %@", [foo valueForKey:@"name"]) ;
    [moc executeFetchRequest:fetchRequest
                       error:NULL] ;
    NSLog(@"2000 name of foo: %@", [foo valueForKey:@"name"]) ;

    // Re-insert the Foo into the moc
    [moc insertObject:foo] ;
    NSLog(@"3000 name of foo: %@", [foo valueForKey:@"name"]) ;

    [moc release] ;
    [mom release] ;
    [pool release] ;

    return 0;
}


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