How Come I Can Cast to Nsmanagedobject But Not to My Entity's Type

How come I can cast to NSManagedObject but not to my entity's type?

Make sure your Class name field is actually Module.Task, where Module is the name of your app. CoreData classes in Swift are namespaced. Right now, your object is being pulled out of the context as an NSManagedObject, not as a Task, so the as-cast is failing.

Core Data Migration: Could not cast value of type 'NSManagedObject_MyType' to 'MyModule.MyType'

The reason is that during migration, you should not be using instances of NSManagedObject subclasses. You need to express all of these in the form of NSManagedObject. So the code above must become:

class LegacyToModernPolicy: NSEntityMigrationPolicy {

static func find(entityName: String,
                 in context: NSManagedObjectContext,
                 sortDescriptors: [NSSortDescriptor],
                 with predicate: NSPredicate? = nil,
                 limit: Int? = nil) throws -> [NSManagedObject] {

    let fetchRequest: NSFetchRequest<NSManagedObject> = NSFetchRequest(entityName: entityName)
    fetchRequest.predicate = predicate
    fetchRequest.sortDescriptors = sortDescriptors
    if let limit = limit {
        fetchRequest.fetchLimit = limit
    }

    do {
        let results = try context.fetch(fetchRequest)
        return results
    } catch {
        log.error("Error fetching: \(error.localizedDescription)")
        throw error
    }
}

func libraryForManager(_ manager: NSMigrationManager) -> NSManagedObject {

    do {
        var library: NSManagedObject? = try LegacyToModernPolicy.find(entityName: Library.entity().name!,
                                                in: manager.destinationContext,
                                                sortDescriptors: [NSSortDescriptor(key: "filename", ascending: true)],
                                                with: nil,
                                                limit: 1).first
        if library == nil {
            let dInstance = NSEntityDescription.insertNewObject(forEntityName: Library.entity().name!, into: manager.destinationContext)

            // awakeFromInsert is not called, so I have to do the things I did there, here:
            dInstance.setValue(Library.libraryFilename, forKey: #keyPath(Library.filename))
            dInstance.setValue(NSDate(timeIntervalSince1970: 0), forKey: #keyPath(Library.updatedAt))
            library = dInstance
        }

        return library!

    } catch {
        fatalError("Not sure why this is failing!")
    }
}}

You can read more about my less-than-fun experiences with Core Data Migrations here.

Problems casting NSManagedObject to subclass type

The cast isn't your problem. Casting doesn't change what class an object is — just what the compiler thinks it is.

You object is an NSManagedObject but not a Contact instance. In you code the object you have is a Hospital entity. Double-check that the Hospital entity is set to use the Contact class (or a subclass)).

It is important to note that Entity inheritance and Objective-C class inheritance don't have to match. I.e. you can have Hospital be a subentry of Contact and still have the Contact entity map to a Contact class without Hospital map to a subclass of the Contact class. It is valid for the Hospital entity to map to the (same) Contact class or even to NSManagedObject (which is what I suspect you've done).

This may seem confusing but can be very powerful if used correctly.

Core Data NSManagedObject downcast with XCode 7 and Swift

Go to your cdatamodel..where you declared your entity..There is a Default Configuration below the Entity. Check the Class column against your entity. By default this will have a dot prefixed. Remove the dot prefix .And it should work. And from what i see is you do not have to prefix your entity class name with the module name in Xcode 7. Hence you cannot use a dot in the class name.I am a newbie in iOS development. So i might not be totally right. But removing the dot prefix solved my issue in Xcode 7.

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