Subclassing NSManagedObject

FROM : Michael Grützner
DATE : Mon Dec 31 11:46:49 2007

Hi List,

I have created a class MyEntity which is a subclass of 
NSManagedObject. The Entity contains
one attribute ("name") and one to-many relationship ("myRelation").
In MyEntity I override the following two methods and I have one 
initWithName: method:

- (id) valueForKey:(NSString *)key;  {
   return [super valueForKey:key];
}

- (void) setValue: (id)value forKey: (NSString *)key {
   [super setValue:value forKey:key];
}

- (id) initWithName: (NSString *) newName {
   self = [super init];
   
   if(self)
       [self setValue:newName forKey:@"name"];
   
   return self;
}


Then I try to add an instance of MyEntity to an NSArrayController via 
addObject: with the code:

MyEntity *entity = [[MyEntity alloc] initWithName:@"My Name"];
[super addObject:entity];

While adding the object to the NSArrayController I get the following 
exception:

[<MyEntity 0x183310> setValue:forUndefinedKey:]: the entity (null) is 
not key value coding-compliant for the key name.

What is the reason for the exception? Do I have to add custom accessor 
methods to MyEntity? If yes, how might these methods
look like for a to-many relationship?

Thank you very much in advance,
Michael