Core Data not saving updates when doing it programatically.
===

I'm using CoreData and I would like to update one of attributes in one of my models, but I can't get it to work using dot notation. My update action looks like this:

    - (void)addNewsPostToFavourites:(UIButton *)sender
    {
        // Returns the right id.
        NSLog(@"Sender tag: %d", sender.tag);

        NSNumber *newsPostId = [NSNumber numberWithInt:sender.tag];
        NewsPost *currentNewsPost = [NewsPost findFirstByAttribute:@"newsPostId" withValue:newsPostId]; 
        // Doesn't seem to do anything.
        currentNewsPost.favourite = @"true";  
    }

I have also tried `[currentNewsPost setValue:@"true" forKey:@"currentNewsPost.favourite"];` but that gives me the same result, nothing happens. 

I therefore wonder what I'm doing wrong. 

Should also mention that I use RestKit in my project too.

Any tips would be appreciated.   