'An NSManagedObject of class 'className' must have a valid NSEntityDescription.' error

I've created simple entity 'CDWorkout' with one attribute 'name' inside CDModel.xcdatamodeld. Name of container in AppDelegate is also 'CDModel'. Class Codegen for 'CDWorkout' is Category/Extension. Here is code for CDWorkout class:

class CDWorkout: NSManagedObject {

class func createWorkout(workoutInfo : Workout, in context: NSManagedObjectContext) -> CDWorkout{
let workout = CDWorkout(context: context)
workout.name = "anyName"
return workout
}
}

the createWorkout function is called from another viewController with context argument as `container.viewContext` but it immediately crashes with message:

> Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'An NSManagedObject of class 'Workout_Generator.CDWorkout' must have a valid NSEntityDescription.'

What did i forget about?

What fixed it for me was that I had an empty space in the name and didn't notice because of a line break. Removing it fixed the problem..

It was:

container = `NSPersistentContainer(name: "ContainerName ")`

Instead of:

container = NSPersistentContainer(name: "ContainerName")

For me this worked,

Adding

@objc('YourEntityClassName')

above the class declaration in 'YourEntityClassName+CoreDataClass' file.

Note: I am using this in an SPM package.

In my case, I had my Core Data model inside a Swift Package and had to follow [this][1] amazing guide and finally this is what did it:

I opened the model and selected the entity and in the right panel I selected the `Data Model Inspector` and in the Class panel, I manually entered the Module’s name i.e. the Swift Package name.

[1]:

[To see links please register here]

In `AppDelegate` check persistent container name.

```swift
let container = NSPersistentContainer(name: "CoreData")
````

If you trying to reach nonexistent `Core Data`, that may manifest as this error.

Name should be exact same as `.xcdatamodeld` object in navigation menu.

I've got the same issue. In my case I used CoreData initialised and managed in framework wich I integrated with main app via **SPM**.

## Solution ##

First, in the framework provide module name for entity by hand, by following steps:
1. open .xcdatamodel,
2. select Entity which you want to edit,
3. open **Data Model Inspector** (the 4th panel in right sidebar),
4. at section **Class** element Module by default presents **Current Product Module** -- enter here your Module name

Repeat these steps for each entity.

Second, in the framework override `description` for each NSManagedObject you use in project, f.ex. you have:

public class Person: NSManagedObject {

}

override there description with String without module name, like:

public class Person: NSManagedObject {

public override var description: String {
return "Person"
}
}

Code presented above will help if you use convenience initialiser for Person (like `Person(context: Context)`) which uses `description` to specify `Person.entity()`.

The issue I had was that I needed to have the _Class Module_ set to _Current Product Module_ for my _CDWorkout_ Entity.

In Xcode 10 there is a drop down in the Class section of the Data Model Inspector.

I encountered this issue using Swift Package Manager to import a Swift Package that had a model file included as a resource. In my case setting the Module of my entity to `Current Production Module` produced an incorrect value in the model file. When I used the debugger to print the model after loading the persistent container the fully qualified class name was something like `Module_Module.Class` instead of the expected `Module.Class`. I had to manually type the module name instead of using `Current Production Module` to resolve the issue.

For me, I forgot to add @objc(Reminder) in this below example. I wrote the NSManagedObject class programmatically.

@objc(Reminder)
public class Reminder: NSManagedObject {


}

One way this could happen is by trying to rename your entities. Make sure that these are the same!

<img src="https://i.stack.imgur.com/86z4N.png" width="600">