Enabling Core data into existing Project does not work

Question

I have created a Project in Xcode 5.1.1 without core data support.

Now i am trying to get the core data support.

Steps:

1) File -> New -> File -> Data Model -> Added.

 It created : samplecd.xcdatamodeld

2) Added Entity:

 myname type: String

3)

To do the changes in the AppDelegate.h and AppDelegate.m,
I have created one more project with 'core data' enabled, and copied
the below contents into the previous project.

AppDelegate.h

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

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

AppDelegate.m

 - (void)saveContext

 {

  NSError *error = nil;

  NSManagedObjectContext *managedObjectContext = self.managedObjectContext;

  if (managedObjectContext != nil) {

    if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {

        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();

    } 

}

}

#pragma mark - Core Data stack

// 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] init];
        [_managedObjectContext setPersistentStoreCoordinator:coordinator];
    }
    return _managedObjectContext;
}





- (NSManagedObjectModel *)managedObjectModel
{
    if (_managedObjectModel != nil) {
        return _managedObjectModel;
    }
    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"withcoredata" withExtension:@"momd"];
    _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
    return _managedObjectModel;
}


- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
    if (_persistentStoreCoordinator != nil) {
        return _persistentStoreCoordinator;
    }

    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"withcoredata.sqlite"];

    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;
}



#pragma mark - Application's Documents directory

// Returns the URL to the application's Documents directory.
- (NSURL *)applicationDocumentsDirectory
{
    return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}

ERROR:

I get the below compilation error:

"AppDelegate.m:122:35: Receiver 'NSManagedObjectContext' for class message is a forward declaration"

 AppDelegate.m:122:34: Receiver type 'NSManagedObjectContext' for instance message is a forward declaration

How to solve this issue?

Answer 1

You need to import CoreData/CoreData.h in your AppDelegte.h file:

#import <CoreData/CoreData.h>

and in YourApp-Prefix.pch:

#ifdef __OBJC__
    #import <UIKit/UIKit.h>
    #import <Foundation/Foundation.h>
    #import <CoreData/CoreData.h>
#endif

Answer 2

your core data model name is samplecd and your sqlite database name is withcoredata both name should be similar for using core data in existing project. Change the name and let me know if your problem is solved or not.