Re: Subclassing NSManagedObject

FROM : Mike Abdullah
DATE : Mon Dec 31 12:43:04 2007

Please read the documentation on -[NSManagedObject 
initWithEntity:insertIntoManagedObjectContext:]

Mike.

On 31 Dec 2007, at 10:46, Michael Grützner wrote:

> 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
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