CODEWITHSUNDEEP
iphoneiosobjective-cxcodeios6
jacobronniegeorge
jacobronniegeorge

Reputation: 555

Creating an Interface for CoreData

Currently I have created a Objective-C Class( NSObject) to handle any special functions that I need, that involve interaction with my CoreData model. These functions that interact with my CoreData are located in dbInterface.h and dbInterface.m files. In the dbInterface class I have added a conform <NSFetchedResultsControllerDelegate>.

@interface dbInterface : NSObject<NSFetchedResultsControllerDelegate>{
    NSFetchedResultsController *fetchedResultsController;
    NSManagedObjectContext *managedObjectContext;
}

And in the app delegate I have created an instance of this class, and connected the delegate managed context with the dbInterface object managed context:

appDelegate.h:

@property (nonatomic, retain) IBOutlet dbInterface *dbConnector;

appDelegate.m:

@synthesize dbConnector;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    dbConnector.managedObjectContext=self.managedObjectContext;
    return YES;
}

Question : I have 6 view controllers which must interact with this dbInterface object, to gather data for the view controller itself. So in this setup the dbInterface is acting as a middleman for the viewController and CoreData model. Is this the right way to perform these specific operations I have defined in the middleman, the dbInterface class?

If it is NOT the right way, then how should I go about interacting with the CoreData model for the view controllers sake?

If it is correct then how do I get access to the object that I declared in the app delegate dbConnector ? Obviously I do not want to create 6 copies of dbInterface class. This has the problem of using too much memory and then having to also write 6 copies of this line:

dbConnector.managedObjectContext=self.managedObjectContext;

I have heard the term singleton bandied about, is this the way to go?

Upvotes: 0

Views: 94

Answers (1)

Hobbes the Tige
Hobbes the Tige

Reputation: 3821

You should be able to reference the instance of your class from your app delegate. Here is the code that I use to reference my app delegate from another class. You'll have to change your class prefix to whatever you use.

#import "NXAppDelegate.h"
NXAppDelegate *appDelegate = (NXAppDelegate *)[[UIApplication sharedApplication] delegate];

Since you're using dbConnector as a property, you can reference it from the app delegate (example below):

viewController.managedObjectContext = appDelegate.dbConnector.managedObjectContext;

Using a singleton is frowned upon a little is iOS development. It has a tendency to be over-used or used without really needing to. If you have evaluated your conditions and cannot use delegates, protocols or subclassing to accomplish your needs, I would suggest using a singleton.

It looks like Apple has updated their documentation to help explain the proper use of singletons if you would like to read up on the topic.

http://developer.apple.com/library/mac/#documentation/General/Conceptual/DevPedia-CocoaCore/Singleton.html

Also, there are plenty of articles online to talk about the pros/cons of singletons.

http://jason.agostoni.net/2012/01/22/ios-best-practices-singletons/

Upvotes: 1

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