Fetch data from CoreData in iOS10, Swift3

There are lots of posting and blog about core data. But there were many changes in core data especially. (At least iOS 10 and Swift 3) Some posting was not useful for me, so I tried many way. Finally I found working codes.

1. Data Model
   In this example, model is very simple. Only one Entity with some attributes and there is no relationships.
   
2. Default codes created by Xcode in AppDelegate.swift

   </pre>
   lazy var persistentContainer: NSPersistentContainer = {
   
   /*
   
   The persistent container for the application. This implementation
   
   creates and returns a container, having loaded the store for the
   
   application to it. This property is optional since there are legitimate
   
   error conditions that could cause the creation of the store to fail.
   
   */
   
   let container = NSPersistentContainer(name: "CheckOutBook")
   
   container.loadPersistentStores(completionHandler: { (storeDescription, error) in
   
   if let error = error as NSError? {
   
   // Replace this implementation with code to handle the error appropriately.
   
   // fatalError() 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.
   
   &nbsp;
   
   /*
   
   Typical reasons for an error here include:
   
   * The parent directory does not exist, cannot be created, or disallows writing.
   
   * The persistent store is not accessible, due to permissions or data protection when the device is locked.
   
   * The device is out of space.
   
   * The store could not be migrated to the current model version.
   
   Check the error message to determine what the actual problem was.
   
   */
   
   fatalError("Unresolved error \(error), \(error.userInfo)")
   
   }
   
   })
   
   return container
   
   }()
   
   // MARK: - Core Data Saving support
   
   func saveContext () {
   
   let context = persistentContainer.viewContext
   
   if context.hasChanges {
   
   do {
   
   try context.save()
   
   } catch {
   
   // Replace this implementation with code to handle the error appropriately.
   
   // fatalError() 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.
   
   let nserror = error as NSError
   
   fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
   
   }
   
   }
   
   }
   <pre>
   
   

3. Fetch Library Item

   func fetchLibraryList() -> [LibraryItem]? {
    // context = self.persistentContainer.viewContext
    let context = getContext();
   
    let fetchRequest : NSFetchRequest<NSFetchRequestResult> = LibraryItem.fetchRequest();
    let entityDescription = NSEntityDescription.entity(forEntityName: "LibraryItem", in: context);
    fetchRequest.entity = entityDescription;
    //fetch.predicate = NSPredicate(format: "checkin_date = nil");
   
    var fetchedObjects : [LibraryItem]? = nil;
    do {
    fetchedObjects = try context.fetch(fetchRequest) as? [LibraryItem];
    }
    catch {
    print("Error in fetching data from core data");
    }
   
    return fetchedObjects;
    }