Creating a singleton with allocWithZone:

BNRItemStore is a singleton, and I was confused on why super allocWithZone: must be called instead of plain old super alloc. And then override alloc instead of allocWithZone.

#import "BNRItemStore.h"

@implementation BNRItemStore

+(BNRItemStore *)sharedStore {
    static BNRItemStore *sharedStore = nil;

    if (!sharedStore)
        sharedStore = [[super allocWithZone: nil] init];

    return sharedStore;
}

+(id)allocWithZone:(NSZone *)zone {
    return [self sharedStore];
}

@end