Problem mit Core Data [NSEntityDescription attributesByName]

[Dylans Ghost]

Hallo,
ich hab' einen unerwarteten runtime error produziert.

-(void)imageSelection: (NSNotification*)notification

{
NSArray *selectedObjects = [[self wavesControllerOutlet] selectedObjects];
if([selectedObjects count] == 0)
{
NSLog(@"updateSelection: [selectedObjects count] = 0 \n ");
return;
}
[self setWavesEntityDescription:[selectedObjects objectAtIndex:0]];
if(NO) NSLog(@"wavesEntityDescription: %@\n",[self wavesEntityDescription]);
}

Bis hierher ist alles ok.

-(id)wavesObjectForKey: (NSString*)key
{
NSDictionary *dict = [[self wavesEntityDescription]attributesByName];
if(YES)NSLog(@"%@\n",dict);
return [dict objectForKey:key];;
}

runtime error:
2012-09-25 00:26:50.712 GiveMeFive[19124:303] -[NSManagedObject attributesByName]: unrecognized selector sent to instance 0x101b3dd30
Was hat in diesem Kontext 'NSManagedObject zu suchen ?'
Ich hab' die Methode aus der NSEntitDescription Class Reference für OS X 10.4 kopiert.

Wer weiss was ?
Uwe