Category on NSEntityDescription to set the correct persistent store

NSEntityDescription+Toolbox.h

//
//  NSEntityDescription+Toolbox.h
//  
//
//  Created by Rabe Bernd on 02.07.12.
//  Copyright (c) 2012 RABE_IT Services. All rights reserved.
//

#import <CoreData/CoreData.h>

@interface NSEntityDescription (Toolbox)
+ (id)insertNewObjectForEntityForName:(NSString *)entityName inManagedObjectContext:(NSManagedObjectContext *)context assignPersistentStoreSkipDefaultConfiguration:(BOOL)assign;
@end

NSEntityDescription+Toolbox.m

//
//  NSEntityDescription+Toolbox.m
//  
//
//  Created by Rabe Bernd on 02.07.12.
//  Copyright (c) 2012 RABE_IT Services. All rights reserved.
//

#import "NSEntityDescription+Toolbox.h"

#define kConfigurationDefault @"PF_DEFAULT_CONFIGURATION_NAME"

@implementation NSEntityDescription (Toolbox)

+ (id)insertNewObjectForEntityForName:(NSString *)entityName inManagedObjectContext:(NSManagedObjectContext *)context assignPersistentStoreSkipDefaultConfiguration:(BOOL)assign
{
    id object = [NSEntityDescription insertNewObjectForEntityForName:entityName inManagedObjectContext:context];
    
    if (assign && nil == [[object objectID] persistentStore]) {
        NSString *entityName = [[object entity] name];
        NSPersistentStoreCoordinator *psc = context.persistentStoreCoordinator;
        NSManagedObjectModel *mom = [psc managedObjectModel];
        
        NSPersistentStore *store = nil;
        for (NSString *configuration in [mom configurations])
        {
            if (![configuration isEqualToString:kConfigurationDefault]) {
                NSString *configName = configuration;
                NSArray *objectNamesForConfiguration = [[mom entitiesForConfiguration:configuration] valueForKeyPath:@"name"];
                NSUInteger index = [objectNamesForConfiguration indexOfObjectPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
                    return [(NSString *)obj isEqualToString:entityName];
                }];
                if (index != NSNotFound) {
                    NSArray *persistentStores = [psc persistentStores];
                    
                    NSUInteger psIndex = [persistentStores indexOfObjectPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
                        return [((NSPersistentStore *)obj).configurationName isEqualToString:configName];
                    }];
                    if (psIndex != NSNotFound) {
                        store = [persistentStores objectAtIndex:psIndex];
                        [context assignObject:object toPersistentStore:store];
                    }
                }
            }
        }
    }
    return object;
}

@end