Stack.h

//
//  Stack.m
//
//  Created by Joshua Howland on 6/12/14.
//  Copyright (c) 2014 DevMountain. All rights reserved.
//


#import <Foundation/Foundation.h>
@import CoreData;

@interface Stack : NSObject

+ (Stack *)sharedInstance;

@property (nonatomic, strong, readonly) NSManagedObjectContext *managedObjectContext;

@end

Stack.m

//
//  Stack.m
//
//  Created by Joshua Howland on 6/12/14.
//  Copyright (c) 2014 DevMountain. All rights reserved.
//

#import "Stack.h"

@interface Stack ()

@property (nonatomic, strong) NSManagedObjectContext *managedObjectContext;

@end

@implementation Stack

+ (Stack *)sharedInstance {
    static Stack *sharedInstance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sharedInstance = [[Stack alloc] init];
    });
    return sharedInstance;

}

- (id)init {
    self = [super init];
    if (self) {
        [self setupManagedObjectContext];
    }
    return self;
}

- (void)setupManagedObjectContext
{
    self.managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
    self.managedObjectContext.persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:self.managedObjectModel];

    NSError* error;
    [self.managedObjectContext.persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType
                                                                       configuration:nil
                                                                                 URL:self.storeURL
                                                                             options:nil
                                                                               error:&error];
    if (error) {
        NSLog(@"error: %@", error);
    }
    
    self.managedObjectContext.undoManager = [[NSUndoManager alloc] init];
}

- (NSURL*)storeURL
{
    NSURL* documentsDirectory = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:YES error:NULL];
    return [documentsDirectory URLByAppendingPathComponent:@"db.sqlite"];
}

- (NSURL*)modelURL
{
    return [[NSBundle mainBundle] URLForResource:@"Model" withExtension:@"momd"];
}

- (NSManagedObjectModel*)managedObjectModel
{
    return [[NSManagedObjectModel alloc] initWithContentsOfURL:self.modelURL];
}

@end