Xcode 8 How to use Core Data Code Gen Classes in Objective-C?

Question

I was watching this tutorial to use Core Data in Xcode 8 and the video was using Swift. In the video, He entered an entity named Task in the Core Data model and then in the code he was able to call Task like:

let task = Task(context: context)

I have an entity called Tag. How can I access Tag in code using Objective-C? Codegen is set in the Core Data model but I don't see any additional files in my project. If I try:

Tag test = [[Tag alloc] init];

I get an error that Tag does not exist.

Answer 1

1. Select the entity 'Tag' in model editor.

2. Generate source code for Task by selecting menu tree 'Editor' -> 'Create NSManagedObject Subclass...' then follow the instruction.

'Tag+CoreDataClass.h'

'Tag+CoreDataClass.m'

'Tag+CoreDataProperties.h'

'Tag+CoreDataProperties.m'

files will be created and automatically will be attached to your project.

3. Import header file.

   #import "Tag+CoreDataProperties.h"
   

4. Then create 'Tag' class.

   NSManagedObjectContext *wContext = ((AppDelegate *)UIApplication.sharedApplication.delegate).persistentContainer.viewContext;
   Tag *wTag = [[Tag alloc] initWithContext:wContext];
   wTag.name = @"TEST";
   

Answer 2

If Codegen is set to "Class Definition" then you can just import your entity's NSManagedObject subclass header file.

Import:

#import "Tag+CoreDataClass.h"

Then the creation of your Tag object will be recognized.

Tag *tag = [NSEntityDescription insertNewObjectForEntityForName:@"Tag" inManagedObjectContext:[self managedObjectContext];
tag.name = @"Tag Name";

Note: If you want to see the files that were generated on your behalf, you can check the DerivedData folder for your project. You should not edit these files or import them into your project.

Something like:

/Users/{Username}/Library/Developer/Xcode/DerivedData/{Your Project Name}/Build/Intermediates/{Your Project Name}.build/Debug-iphonesimulator/{Your Project Name}.build/DerivedSources/CoreDataGenerated/{Your Project Name}/

There are other Codegen options that offer different options depending on your use case:

• None/Manual: Allows you to manage the NSManagedObject subclasses yourself. With this option, you will see the files in your project and you can modify them.
• Category/Extension: Allows you to have custom properties (attributes) that you do not want Core Data to manage.

I posted a more detailed answer regarding Codegen options here: https://stackoverflow.com/a/40647786/4748172