How to add Core Data to my project and store the data getting from JSON service

Question

i am doing in appDelegate.h like this

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

- (void)saveContext;
- (NSURL *)applicationDocumentsDirectory;

and implementinig all these things in appDelegate.m

Answer 1

That's a pretty big question to handle, but typically you'd add something like this (if you're using UIManagedDocument) to your appdelegate.m's - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions:

NSFileManager *fileManager = [NSFileManager defaultManager];
NSURL *documentsDirectory = [[fileManager URLsForDirectory:NSDocumentDirectory
                                                 inDomains:NSUserDomainMask] firstObject];
NSString *documentName = @"YOUR_DATABASE_NAME";
NSURL *url = [documentsDirectory URLByAppendingPathComponent:documentName];
self.document = [[UIManagedDocument alloc] initWithFileURL:url];

BOOL fileExists = [fileManager fileExistsAtPath:[url path]];
if (fileExists) {
    [self.document openWithCompletionHandler:^(BOOL success) {
        if (success) {
            self.context = self.document.managedObjectContext;
            // Post notification so others can gather the document and context
            [[NSNotificationCenter defaultCenter] postNotificationName:@"DatabaseReady"
                                                                object:self];
        }
        if (!success) NSLog(@"couldn't open file at %@", url);
    }];
} else {
    [self.document saveToURL:url
            forSaveOperation:UIDocumentSaveForCreating
           completionHandler:^(BOOL success) {
               if (success) {
                   self.context = self.document.managedObjectContext;
                   // Post notification so others can gather the document and context
                   [[NSNotificationCenter defaultCenter] postNotificationName:@"DatabaseReady"
                                                                       object:self];
               }
               if (!success) NSLog(@"couldn't open file at %@", url);
           }];
}

You should put @property (strong, nonatomic) UIManagedDocument *document; in your appdelegate's .h file so that other view controllers can get the document. In view controllers that need to contact the database in some way, add this:

- (void)awakeFromNib
{
    // Listen for UIManagedDocument so that we can get the database set up right
    // This only works in awakeFromNib (viewDidLoad is too late)
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(getUIManagedDocument:)
                                                 name:@"DatabaseReady"
                                               object:nil];
}

Then, you'll need to add the getUIManagedDocument: method to your view controller:

- (void)getUIManagedDocument:(NSNotification *)notification
{
    self.document = [(OneWorldAppDelegate *)[[UIApplication sharedApplication] delegate] document];
    self.context = self.document.managedObjectContext;
}

Of course you'll need to add

@property (strong, nonatomic) UIManagedDocument *document;
@property (strong, nonatomic) NSManagedObjectContext *context;

to your files. That's where self.context comes from.

At that point, you are ready to start doing things with your database.

IMPORTANT: Don't forget to #import your appdelegate's .h file in the view controller in which you'd like to access the appdelegate's @property document!

As far as getting JSON data, I recommend that you work through a tutorial, like this one. It explains things quite clearly.

Hope it helps!