ManagedObjectContext

ManagedObjectContext.h

//
//  ManagedObjectContext.h
//
//  Created by Amos, Grant
//

#import <Foundation/Foundation.h>

@interface ManagedObjectContext : NSObject

@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;
@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;

+ (ManagedObjectContext*)sharedInstance;

- (void)saveContext;

@end

ManagedObjectContext.m

//
//  ManagedObjectContext.m
//
//  Created by Amos, Grant
//
 
#import "ManagedObjectContext.h"
 
#define DATABASE_NAME @"MyApp"
 
@implementation ManagedObjectContext
 
@synthesize managedObjectContext = _managedObjectContext;
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;
 
+ (ManagedObjectContext*)sharedInstance
{
    static dispatch_once_t p = 0;
    
    __strong static id _sharedObject = nil;
    
    dispatch_once(&p, ^{
        _sharedObject = [[self alloc] init];
    });
    
    return _sharedObject;
}
 
- (void)saveContext
{
    __weak NSManagedObjectContext *_weakContext = self.managedObjectContext;
    [self.managedObjectContext performBlock:^{
        NSError *error;
        
        [_weakContext save:&error];
        
        if (error)
        {
            NSLog(@"Failed to save context.");
        }
    }];
}
 
// Returns the managed object context for the application.
// If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application.
- (NSManagedObjectContext *)managedObjectContext
{
    if (_managedObjectContext != nil) {
        return _managedObjectContext;
    }
    
    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
    if (coordinator != nil) {
        _managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
        [_managedObjectContext setPersistentStoreCoordinator:coordinator];
    }
    return _managedObjectContext;
}
 
// Returns the managed object model for the application.
// If the model doesn't already exist, it is created from the application's model.
- (NSManagedObjectModel *)managedObjectModel
{
    if (_managedObjectModel != nil) {
        return _managedObjectModel;
    }
    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:DATABASE_NAME withExtension:@"momd"];
    _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
    return _managedObjectModel;
}
 
// Returns the persistent store coordinator for the application.
// If the coordinator doesn't already exist, it is created and the application's store added to it.
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
    if (_persistentStoreCoordinator != nil) {
        return _persistentStoreCoordinator;
    }
    
    NSString *filename = [DATABASE_NAME stringByAppendingString:@".sqlite"];
    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:filename];
    
    NSError *error = nil;
    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error])
    {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }
    
    return _persistentStoreCoordinator;
}
 
// Returns the URL to the application's Documents directory.
- (NSURL *)applicationDocumentsDirectory
{
    return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}
 
@end