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copied!<p>What you are trying to do is often called a "data store" singleton, and it's a good design pattern to use. What I do in my applications is have a singleton class named <code>DataStore</code>, you can call it whatever you wish, with a class method:</p> <pre><code>+ (id)sharedStore{ static DataStore *sharedStore = nil; if (!sharedStore) { sharedStore = [[self alloc] init]; } return sharedStore; } </code></pre> <p>Whenever I need access to the resources provided by the datastore, I do:</p> <pre><code>Datastore *ds = [Datastore sharedStore]; </code></pre> <p>To provide access to Core Data, I have a data store method:</p> <pre><code>+ (NSManagedObjectContext*)managedObjectContext{ static NSManagedObjectContext *context = nil; if(context){ return context; } NSPersistentStoreCoordinator *coordinator = nil; NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"Model" withExtension:@"momd"]; NSManagedObjectModel *objectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL]; if (!coordinator) { coordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:objectModel]; } if(!coordinator){ return nil; } NSString *storePath = [[self documentsDirectoryPath] stringByAppendingPathComponent:@"datastore.sqlite"]; NSURL *storeURL = [NSURL URLWithString:storePath]; NSError *error; if (![coordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:NULL error:&error]) { NSLog(@"Database error: %@", error); // if you make changes to your model and a database already exists in the app // you'll get a NSInternalInconsistencyException exception. When the model is updated // the databasefile must be removed. Remove the database here because it's easy. NSFileManager *fileManager = [NSFileManager defaultManager]; [fileManager removeItemAtURL:storeURL error:nil]; //try to add the persistant store one more time. If it still fails then abort if (![coordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:NULL error:&error]) return nil; } context = [[NSManagedObjectContext alloc] init]; [context setPersistentStoreCoordinator:coordinator]; [context setUndoManager:nil]; return context; } </code></pre> <p>This method returns <code>nil</code> if an <code>NSManagedObjectContext</code> couldn't be created. This way you only need to do:</p> <p><code>NSManagedObjectContext *context = [[DataStore sharedStore] managedObjectContext];</code></p> <p>whenever you need to use Core Data. This can be done once in <code>viewDidLoad</code>. </p> <p>Edit:</p> <p>The <code>managedObjectContext</code> method uses the method below to find the documents directory:</p> <pre><code>+ (NSString *)documentsDirectoryPath { NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil; return basePath; } </code></pre>

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