Adding Core Data to existing iPhone project

Question

I'd like to add core data to an existing iPhone project, but I still get a lot of compile errors:

- NSManagedObjectContext undeclared

 - Expected specifier-qualifier-list before 'NSManagedObjectModel'

 - ...

I already added the Core Data Framework to the target (right click on my project under "Targets", "Add" - "Existing Frameworks", "CoreData.framework").

My header-file:

NSManagedObjectModel *managedObjectModel;
NSManagedObjectContext *managedObjectContext;       
NSPersistentStoreCoordinator *persistentStoreCoordinator;

[...]

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

What am I missing? Starting a new project is not an option...

Thanks a lot!

edit sorry, I do have those implementations... but it seems like the Library is missing... the implementation methods are full with compile error like "managedObjectContext undeclared", "NSPersistentStoreCoordinator undeclared", but also with "Expected ')' before NSManagedObjectContext" (although it seems like the parenthesis are correct)...

#pragma mark -
#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;
}


/**
 Returns the managed object model for the application.
 If the model doesn't already exist, it is created by merging all of the models found in    
 application bundle.
 */
- (NSManagedObjectModel *)managedObjectModel {

    if (managedObjectModel != nil) {
        return managedObjectModel;
    }
    managedObjectModel = [[NSManagedObjectModel mergedModelFromBundles:nil] retain];    
    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;
    }

    NSURL *storeUrl = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] 
        stringByAppendingPathComponent: @"Core_Data.sqlite"]];

    NSError *error = nil;
    persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] 
    initWithManagedObjectModel:[self managedObjectModel]];
    if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType 
    configuration:nil URL:storeUrl options:nil error:&error]) {
    /*
     Replace this implementation with code to handle the error appropriately.

     abort() causes the application to generate a crash log and terminate. You should 
    not use this function in a shipping application, although it may be useful during 
    development. If it is not possible to recover from the error, display an alert panel that 
    instructs the user to quit the application by pressing the Home button.

     Typical reasons for an error here include:
     * The persistent store is not accessible
     * The schema for the persistent store is incompatible with current managed object 
                model
     Check the error message to determine what the actual problem was.
     */
    NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    abort();
}    

return persistentStoreCoordinator;
}

Answer 1

+(void) insetPlusUpdate:(NSDictionary *)dataa {

    NSManagedObjectContext * context;

    if (![[NSThread currentThread] isMainThread]) {

        context = [[NSManagedObjectContext alloc] init];

        [context setPersistentStoreCoordinator:[APP_DELEGATE persistentStoreCoordinator]];
    } else {

        context = [APP_DELEGATE managedObjectContext];
    }

    NSFetchRequest * request = [[NSFetchRequest alloc] init];

    NSEntityDescription * entity = [NSEntityDescription entityForName:@"EntityName" inManagedObjectContext:context];

    [request setEntity:entity];

    NSPredicate * check = [NSPredicate predicateWithFormat:@"attribute == %@", Dict[@"key"]];

    [request setPredicate:check];

    NSError * error = nil;

    if ([context countForFetchRequest:request error:&error] == 0) {

Entity.attribute = @"";

    } else {


        NSArray * array = [context executeFetchRequest:request error:&error];

        EntityName * entity = [array firstObject];

  Entity.attribute = @"";

    }

}

+(NSString *)fetch:(NSString *)feed_id{

    NSManagedObjectContext * context;

    if(![[NSThread currentThread] isMainThread]){

        context = [[NSManagedObjectContext alloc] init];

        [context setPersistentStoreCoordinator:[APP_DELEGATE persistentStoreCoordinator]];

    } else {

        context = [APP_DELEGATE managedObjectContext];

    }

    NSFetchRequest * request = [[NSFetchRequest alloc] init];

    NSEntityDescription * entity = [NSEntityDescription entityForName:@"ENTITYNAME" inManagedObjectContext:context];

    [request setEntity:entity];

   NSPredicate * check = [NSPredicate predicateWithFormat:@"attribute == %@", Dict[@"key"]];

    [request setPredicate:check];

    NSError * error = nil;

    if ([context countForFetchRequest:request error:&error] > 0) {

        NSArray * array = [context executeFetchRequest:request error:&error];

        ENTITYNAME * fetchData = [array firstObject];

        NSString * string = fetchData.attribte[@"key"];

        return string;
    }

    return nil;
}


+(BOOL)delete{

    NSManagedObjectContext * context;

    if (![[NSThread currentThread] isMainThread]) {

        context = [[NSManagedObjectContext alloc] init];

        [context setPersistentStoreCoordinator:[APP_DELEGATE persistentStoreCoordinator]];

    } else {

        context = [APP_DELEGATE managedObjectContext];

    }

    NSFetchRequest * request = [[NSFetchRequest alloc] init];

    NSEntityDescription * entity = [NSEntityDescription entityForName:@"ENTITYNAME" inManagedObjectContext:context];

    [request setEntity:entity];

    NSError *error = nil;

    NSBatchDeleteRequest *deleteRequest = [[NSBatchDeleteRequest alloc] initWithFetchRequest: request];

    @try{

        [context executeRequest:deleteRequest error:&error];
        if([context save:&error]){

            NSLog(@"Deleted");

            return [context save:&error];

        }
        else{

            return [context save:&error];
        }

    }
    @catch(NSException *exception){

        NSLog(@"failed %@",exception);
        return [context save:&error];
    }    


}

Answer 2

Try creating Core Data backed Cocoa application and look at AppDelegate. You'll see core data stack implementation methods there as well as managed object model file for defining your entities and other core-data releated stuff.

You've shown us only header (i.e. declaration), but not implementation (i.e. definition) of the Core Data stack.

Answer 3

As Eimantas stated your missing the implementiation of the Core Stack, like

- (NSManagedObjectContext *) managedObjectContext;
- (NSManagedObjectModel *)managedObjectMode;
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator;

On solution would be to create a new core data driver project and copy / paste the implementation to your project.

Answer 4

  - (void)viewDidLoad {
  [super viewDidLoad];
  // Do any additional setup after loading the view.
   if (self.userData) {
    [self.nameTxt setText:[self.userData valueForKey:@"name"]];
    [self.mobileTxt setText:[self.userData 
     valueForKey:@"mobileNumber"]];
    [self.emailIdTxt setText:[self.userData valueForKey:@"email"]];
    [self.imgView setImage:[UIImage imageWithData:[self.userData 
     valueForKey:@"imageView"]]];    }
        }

  - (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
  }


  - (BOOL)textFieldShouldReturn:(UITextField *)textField
  {
   [textField resignFirstResponder];
return YES;
 }
  /*
  #pragma mark - Navigation



 - (IBAction)browseBtn:(id)sender
   {

  UIImagePickerController *imgpic =[[UIImagePickerController      
     alloc]init];     
  imgpic .delegate =self;
 imgpic .sourceType =UIImagePickerControllerSourceTypePhotoLibrary;
[self presentViewController:imgpic animated:YES completion:nil];

 }
 -(void)imagePickerController:(UIImagePickerController *)picker 
 didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info
 {
  UIImage *choose = info[UIImagePickerControllerOriginalImage];
self.imgView.image=choose;
[picker dismissViewControllerAnimated:YES completion:nil];
}


  - (IBAction)saveBtnClick:(id)sender {

 NSManagedObjectContext *context = [self managedObjectContext];

 if (self.userData) {
    // Update existing data
    [self.userData setValue:self.nameTxt.text forKey:@"name"];
    [self.userData setValue:self.mobileTxt.text 
     forKey:@"mobileNumber"];        
   [self.userData setValue:self.emailIdTxt.text forKey:@"email"];

    UIImage *sampleimage = _imgView.image;
    NSData *dataImage = UIImageJPEGRepresentation(sampleimage, 1.0);
            [self.userData setValue:dataImage forKey:@"imageView"];

    } else {
    // Create a new data
    NSManagedObject *newDevice = [NSEntityDescription 
     insertNewObjectForEntityForName:@"Details" 
     inManagedObjectContext:context];
    [newDevice setValue:self.nameTxt.text forKey:@"name"];
    [newDevice setValue:self.mobileTxt.text forKey:@"mobileNumber"];
    [newDevice setValue:self.emailIdTxt.text forKey:@"email"];
    UIImage *sampleimage = _imgView.image;
    NSData *dataImage = UIImageJPEGRepresentation(sampleimage, 1.0);

    [newDevice setValue:dataImage forKey:@"imageView"];

  }

  NSError *error = nil;
 // Save the object to persistent store
 if (![context save:&error]) {
    NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]);
 }

 [self dismissViewControllerAnimated:YES completion:nil];
 }
   @end

.h

 #import <UIKit/UIKit.h>
#import <CoreData/CoreData.h>

 @interface DetailViewController :
 UIViewController<UITextFieldDelegate,UINavigationControllerDelegate,            
     UIIma
    gePickerControllerDelegate>
         @property (weak, nonatomic) IBOutlet UITextField *nameTxt;
  @property (weak, nonatomic) IBOutlet UITextField *mobileTxt;
 @property (weak, nonatomic) IBOutlet UITextField *emailIdTxt;
  @property (weak, nonatomic) IBOutlet UIImageView *imgView;
 - (IBAction)browseBtn:(id)sender;
 - (IBAction)saveBtnClick:(id)sender;
@property (strong,nonatomic) NSManagedObject *userData;

@end

Answer 5

If you run into this same issue in xcode 4, as I did. It is different: I had to select the project, then in targets expand "Link Binary With Libraries" which shows the current libraries. From there click the + (plus sign) to select any additional libraries you need. I placed it in the top of the project and had to move it (drag and drop) to the Frameworks Group, but that was it.

Answer 6

Just to expound on all the steps you actually need to perform to add Core Data to a project that previously did not have it:

Step 1: Add the Framework

Click on your app target (on the left pane its the top icon with the name of your app) then go to the 'Build Phases' tab then on 'Link Binary With Libraries', click the little '+' at the bottom then find 'CoreData.framework' and add it to your project

Then either import coredata on all the objects you need it (the non-sexy way) using:

Swift

import CoreData

Objective C

#import <CoreData/CoreData.h>

or add the import below the common imports in your .pch file (much more sexy) like this:

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

Step 2: Add the Data Model

To add the .xcdatamodel file right click/control-click on your files in the right pane (like in a Resources folder for safe keeping) and select to Add a New File, Click the Core Data tab when selecting your file type then Click 'Data Model', give it a name and click Next and Finish and it will add it to your project. When you click on this Model object you will see the interface to add the Entities to your project with any relationships you want.

Step 3: Update App Delegate

In Swift on AppDelegate.swift

//replace the previous version of applicationWillTerminate with this
func applicationWillTerminate(application: UIApplication) {
    // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
    // Saves changes in the application's managed object context before the application terminates.
    self.saveContext()
}

func saveContext () {
    var error: NSError? = nil
    let managedObjectContext = self.managedObjectContext
    if managedObjectContext != nil {
        if managedObjectContext.hasChanges && !managedObjectContext.save(&error) {
            // Replace this implementation with code to handle the error appropriately.
            // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
            //println("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.
var managedObjectContext: NSManagedObjectContext {
    if !_managedObjectContext {
        let coordinator = self.persistentStoreCoordinator
        if coordinator != nil {
            _managedObjectContext = NSManagedObjectContext()
            _managedObjectContext!.persistentStoreCoordinator = coordinator
        }
    }
    return _managedObjectContext!
}
var _managedObjectContext: NSManagedObjectContext? = nil

// Returns the managed object model for the application.
// If the model doesn't already exist, it is created from the application's model.
var managedObjectModel: NSManagedObjectModel {
    if !_managedObjectModel {
        let modelURL = NSBundle.mainBundle().URLForResource("iOSSwiftOpenGLCamera", withExtension: "momd")
        _managedObjectModel = NSManagedObjectModel(contentsOfURL: modelURL)
    }
    return _managedObjectModel!
}
var _managedObjectModel: NSManagedObjectModel? = nil

// 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.
var persistentStoreCoordinator: NSPersistentStoreCoordinator {
    if !_persistentStoreCoordinator {
        let storeURL = self.applicationDocumentsDirectory.URLByAppendingPathComponent("iOSSwiftOpenGLCamera.sqlite")
        var error: NSError? = nil
        _persistentStoreCoordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
        if _persistentStoreCoordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: storeURL, options: nil, error: &error) == nil {
            /*
            Replace this implementation with code to handle the error appropriately.
            abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
            Typical reasons for an error here include:
            * The persistent store is not accessible;
            * The schema for the persistent store is incompatible with current managed object model.
            Check the error message to determine what the actual problem was.
            If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory.
            If you encounter schema incompatibility errors during development, you can reduce their frequency by:
            * Simply deleting the existing store:
            NSFileManager.defaultManager().removeItemAtURL(storeURL, error: nil)
            * Performing automatic lightweight migration by passing the following dictionary as the options parameter:
            [NSMigratePersistentStoresAutomaticallyOption: true, NSInferMappingModelAutomaticallyOption: true}
            Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details.
            */
            //println("Unresolved error \(error), \(error.userInfo)")
            abort()
        }
    }
    return _persistentStoreCoordinator!
}
var _persistentStoreCoordinator: NSPersistentStoreCoordinator? = nil

// #pragma mark - Application's Documents directory

// Returns the URL to the application's Documents directory.
var applicationDocumentsDirectory: NSURL {
    let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
    return urls[urls.endIndex-1] as NSURL
}

In Objective C make sure to add these objects to AppDelegate.h

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

 - (NSURL *)applicationDocumentsDirectory; // nice to have to reference files for core data

Synthesize the previous objects in AppDelegate.m like this:

@synthesize managedObjectContext = _managedObjectContext;
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;

Then add these methods to AppDelegate.m (make sure to put the name of the model that you added in the spots shown):

- (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();
        }
    }
}

- (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:@"NAMEOFYOURMODELHERE" withExtension:@"momd"];
    _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
    return _managedObjectModel;
}

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

    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"NAMEOFYOURMODELHERE.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];
}

Step 4: Get the Data Objects to the ViewControllers Where You Need the Data

Option 1. Use the App Delegate's ManagedObjectContext from VC (Preferred and Easier)

As suggeted by @brass-kazoo - Retrieve a reference to AppDelegate and its managedObjectContext via:

Swift

 let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
 appDelegate.managedObjectContext

Objective C

 [[[UIApplication sharedApplication] delegate] managedObjectContext];

in your ViewController

Option 2. Create ManagedObjectContext in your VC and have it match AppDelegate's from the AppDelegate (Original)

Only showing old version for Objective C since much easier to use the preferred method

in the ViewController.h

@property (nonatomic, retain) NSManagedObjectContext *managedObjectContext;

In the ViewController.m

@synthesize managedObjectContext = _managedObjectContext;

In the AppDelegate, or class where the ViewController is created set the managedObjectContext to be the same as the AppDelegate one

ViewController.managedObjectContext = self.managedObjectContext;

If you want the viewcontroller using Core Data to be a FetchedResultsController then you'll need to make sure this stuff is in your ViewController.h

@interface ViewController : UIViewController <NSFetchedResultsControllerDelegate> {
  NSFetchedResultsController *fetchedResultsController;
  NSManagedObjectContext *managedObjectContext;
}

 @property (nonatomic, retain) NSFetchedResultsController *fetchedResultsController;

And this is in ViewController.m

@synthesize fetchedResultsController, managedObjectContext;

After all of that you can now use this managedObjectContext to run all the usual fetchRequests needed for CoreData goodness! Enjoy