Question

I would like to know if it’s possible to init a subclass of NSManagedObject ?
I have a class “Actualite” which is a subclass of NSManagedObject and when I want to initialize this class, I get this error :
“CoreData: error: Failed to call designated initializer on NSManagedObject class Actualite”, and the app crashes after this message “-[Actualite setTitre:]: unrecognized selector sent to instance 0x8433be0”

Here is my code :

-(void) recupererActualites {
listeNouvellesActualites = [[NSMutableArray alloc] init];

// Convert the supplied URL string into a usable URL object
NSURL *url = [NSURL URLWithString:FACE06_RSS];

// Create a new rssParser object based on the TouchXML "CXMLDocument" class, this is the
// object that actually grabs and processes the RSS data
CXMLDocument *rssParser = [[CXMLDocument alloc] initWithContentsOfURL:url encoding:NSUTF8StringEncoding options:0 error:nil];

// Create a new Array object to be used with the looping of the results from the rssParser
NSArray *resultNodes = NULL;

// Set the resultNodes Array to contain an object for every instance of an  node in our RSS feed
resultNodes = [rssParser nodesForXPath:@"//item" error:nil];

NSMutableArray* tmp = [[NSMutableArray alloc] init];
for (CXMLElement* resultElement in resultNodes) {
    // Create a temporary MutableDictionary to store the items fields in, which will eventually end up in blogEntries
    NSMutableDictionary *blogItem = [[NSMutableDictionary alloc] init];
    NSMutableArray* categories = [[NSMutableArray alloc] init];

    // Create a counter variable as type "int"
    int counter;

    // Loop through the children of the current  node
    for(counter = 0; counter < [resultElement childCount]; counter++) {
        // Add each field to the blogItem Dictionary with the node name as key and node value as the value
        if([[[resultElement childAtIndex:counter] name] isEqual:@"category"])
            [categories addObject:[[resultElement childAtIndex:counter] stringValue]];
        else {
            if ([[resultElement childAtIndex:counter] stringValue] != nil)
                [blogItem setObject:[[resultElement childAtIndex:counter] stringValue] forKey:[[resultElement childAtIndex:counter] name]];
            else
                [blogItem setObject:@"" forKey:[[resultElement childAtIndex:counter] name]];
        }
    }

    Actualite* actu = [[Actualite alloc] init];
    [blogItem setObject:categories forKey:@"categories"];
    [actu initWithDictionnary:blogItem];
    [tmp addObject:actu];
    //[actu release];

    [categories release];
    [blogItem release];
}
listeNouvellesActualites = tmp;

[rssParser release];
resultNodes = nil;

// Stockage des actualités en local
[self stockerActualites];
}

And the initWithDictionary method set all the attributes of the Actualite class.

I also tried

Actualite* actu = [[Actualite alloc] initWithEntity:[NSEntityDescription entityForName:@"Actualite" inManagedObjectContext:managedObjectContext] insertIntoManagedObjectContext:managedObjectContext]; 

and

Actualite* actu = (Actualite*)[NSEntityDescription entityForName:@"Actualite" inManagedObjectContext:managedObjectContext]; 

instead of

Actualite* actu = [[Actualite alloc] init]; 

The errors disappear but the app stops at this point. I don’t know what can I do…

Is someone already had this problem ?

Thanks a lot !

Answer 1

The idea is that you ask for a new object to be created inside a context and then you use it:

Actualite* actu = [NSEntityDescription insertNewObjectForEntityForName:@"Actualite" inManagedObjectContext:managedObjectContext];