Xcode Is Looking for Core Data Entity Names with Dot; Not Compiling

Error when creating NSManaged Subclass in Xcode 8.2 beta

The issue here is that as of Xcode 8, new projects using Core Data and new Core Data data models are configured to use automatic code generation by default. That means you don’t have to explicitly generate code for your Core Data entities any more, Xcode will take care of that for you. If you leave automatic code generation on and also manaully generate Swift classes for your entities, you’ll see an error like this.

You can disable automatic code generation for an entity in the entity inspector, or you can remove the manually-generated code from your project. Either of the two should fix this.

Cannot create NSManagedObject subclass

You are manually generating a NSManagedObject subclass, which has already been generated by Xcode.

Find detailed solutions here.

How to make Xcode core data code generated files to be public accessed

You should be able to make the automatically generated header files be publicly accessible by copying them from the derived sources folder to the public headers folder of your framework.

You can do this by adding an extra Run Script step to the target of your framework. Copy the following script into the script editor and replace Your_Framework with the name of your frameworks executable.

#set -o xtrace
find "${DERIVED_SOURCES_DIR}/CoreDataGenerated/Your_Framework" -type f -name "*.h" -exec cp {} "${BUILT_PRODUCTS_DIR}/${PUBLIC_HEADERS_FOLDER_PATH}" \;

All this script does is list every header file in the derived sources directory (find $SOURCEPATH -type f -name "*.h") and then calls copy on each one in turn -exec cp {} $DESTPATH \;

If you have any problems uncommenting the first line (i.e. removing the #) and then looking at the build log should make it easier to diagnose.

Duplicate Symbol Error in NSManagedObject Subclass

You are generating files which have already been generated for you by Xcode and thus get duplicate declarations. Details about this feature (new in Xcode 8) can be found in this WWDC video.

Two possible fixes:

1) Use the Xcode generated ManagedObject subclasses (the recommended, modern approach)

• Delete all generated NSManagedObject subclasses from your project, if exists.
• Set Codegento Class Definition in your .xcdatamodel for all entities
• Make sure Module is empty ("Global Namespace" in light gray) (workaround an Apple bug, see this answer)

• Clean project
• Clean DerivedData folder (Optional. To be on the save side)
• build

Note:

Never add the automatically generated files to your project. Even you do not see the generated files in your project, Xcode has a reference to it, so you are able to write extensions and such. For instance:

extension MyEntity {
    func doSomething() {
        //
    }
}

Also, you can command+click to the generated file within Xcode.

2) Trigger subclass generation manually (a rather paranoid but bullet-prove approach, ignoring the new Xcode features)

• Delete all generated NSManagedObject subclasses from your project, if exists.
• Set Codegento Manual/None in your .xcdatamodel for all entities
• Clean project
• Clean DerivedData folder
• Restart Xcode
• Manually generate NSManagedObject subclasses (in "Editor" menu)
• Make sure those files are added to your project
• build

NSManagedObject subclasses duplicate declaration

You are generating files which have already been generated for you by Xcode and thus get duplicate declarations.

Find detailes in this answer.

Core Data Giving Error

The problem here is that your accessor and your ivar have the same name. That's where the underbar ivar convention comes from. Here, you're not using the accessor to access your property, you're using the backing variable directly, so it never gets initialize. Instead, make sure you always go through your accessor methods and you won't have a problem. So, rewrite the offending method (and any others that use the managedContextObject property with something like the following:

- (void)viewWillAppear:(BOOL)animated
{
  [super viewWillAppear:animated]; // it's good practice to call the super methods, even if you're fairly certain they do nothing

  // Get a reference to the managed object context *through* the accessor
  NSManagedObjectContext* context = [self managedObjectContext];

  // From now on, we only use this reference in this method
  NSFetchRequest = [[NSFetchRequest alloc] init];
  NSEntityDescription* entity = [NSEntityDescription entityForName:@"Remind" inManagedObjectContext:context]; // <- use the local reference we got through the accessor
  [request setEntity:entity];
  NSError* error = nil;
  NSArray* array = [context executeFetchRequest:request error:&error];
  if( !array ) {
    // Do something with the error
    NSLog(@"Error Fetching: %@", error);
  }
  [self setDesitnationsArray:[array mutableCopy]];
  [destinationsTableView reloadData];
}

You might want to change your ivars to something you won't be tempted to use or that will be immediately apparent that you haven't gone through the accessors, like _managedObjectContext or even _privateContext or whatever will stick out to you until you get used to accessing properties through the accessors. If you don't like the Objective-C syntax for accessing properties, you could use the dot syntax, but you must always remember to go through self, for example, self.managedObjectContext. I don't like this method as people forget that it's not a direct property access and it is using the accessors, so they think it's okay to interchange the dot syntax for a direct access, when it's not (like in your case).

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