ソフトウェアエンジニアの技術ブログ：Software engineer tech blog

Context (notebook)
-> notification
FetchedResultsController
-> delegate
CoreDataTableViewController
-> update
TableView

saving images(BLOBs) and migrating data model

Importing large sets of objects into the database without blocking the user interface
Downloading new objects from a REST service and inserting them into the db.
Saving datasets in the background since saving can take a user-perceivable amount of time.

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath)-> UITableViewCell{
	
	let note = fetchedResultsController?.object(at: indexPath) as! Note

	let cell = tableView.dequeueReusableCell(withIdentifier: "Note", for: indexPath)

	cell.textLabel?.text = note.text

	return cell
}

override func prepare(for segue: UIStoryboardSeque, sender: Any?){
	
	if segue.identifier! == "displayNote"{
	 	if let notesVC = segue.destination as? NotesViewController {

	 	let fr = NSFetchRequest<NSFetchRequestResult>(entityName: "Note")

	 	fr.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending:false),NSSortDescriptor(key: "text", ascending: true)]

	 	let indexPath = tableView.indexPathForSelectedRow!
	 	let notebook = fetchedResultsController?.object(at: indexPath)

	 	let pred = NSPredicate(format: "notebook = %@", argumentArray: [notebook!])

	 	fr.predicate = pred

	 	let fc = NSFetchedResultsController(fetchRequest: fr, managedObjectContext:fetchedResultsController!.managedObjectContext, sectionNameKeyPath: nil, cacheName: nil)

	 	notesVC.fetchedResultsController = fc
	 	}
	}
}

-How the table displays changes
-How a user can add a new note
-Saving and persisting changes
-Memory management

class CoreDataTableViewController: UITableViewController {
	
	var fetchedResultsController : NSFetchedResultsController<NSFetchRequestsResult>?{
		didSet {
			fetchedResultsController?.delegate = self
			executeSearch()
			tableView.reloadData()
		}
	}

	init(fetchedResultsController fc : NSFetchedResultsController<NSFetchRequestResult>, style: UITableViewStyle = .plain){
		fetchedResultsController = fc
		super.init(style: style)
	}

	required init?(coder aDecoder: NSCoder){
		super.init(coder: aDecoder)
	}
}

class NotebooksViewController: CoreDataTableViewController {
	
	// MARK: Life Cycle

	overeride func viewDidLoad(){
		super.viewDidLoad()

		title = "CoolNotes"

		let delegate = UIApplication.shared.delegate as! AppDelegate
		let stack = delegate.stack

		let fr = NSFetchRequest<NSFetchRequestResult>(entityName: "Notebook")
		fr.sortDescriptors = [NSSortDescriptor(key: "name", ascending: true), NSSortDescriptor(key: "creationDate", ascending: false)]

		fetchedResultsController = NSFetchedResultsController(fetchRequest:  fr, managedObjectContext: stack.context, sectionNameKeyPath: nil, cacheName: nil)

	}

	override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
		let nb = fetchedResultsController!.object(at: indexPath) as! Notebook

		let cell = tableView.dequeueReusableCell(withIdentifier: "NotebookCell", for: indexPath)

		cell.textLabel?.text = nb.name
		cell.detailTextLabel?.text = "\(nb.notes!.count) notes"

		return cell
	}
}

import Foundation
import CoreData

extesion Note {
	@NSManaged var creationDate: NSDate?
	@NSManaged var text: String?
	@NSManaged var notebook: Notebook?
}

import Foundation
import CoreData

extesion NSManagedObject {
	convention init(text:String = "New Note", context: NSManagedObjectContext){
		if let ent = NSEntityDescription.entityForName("Note",
			inManagedObjectContext; context){
			self.init(entity: ent, insertIntoManagedObjectContext: context)
			self.text = text
			self.creationDate = NSDate()
		} else {
			fatalError("Unable to find Entity name!")
		}
	}
}

// Don't worry about the @NSManaged thing.
// it's just a cue to the compiler that the property
// will be managed by Core Date
class Note: NSManagedObject {
	@NSManaged var notebook : Notebook
}

class Notebook: NSManagedObject {
	@NSManaged var note : ????
}

import CoreData
struct CoreDataStack {
	// MARK: - Properties
	private let model : NSManagedObjectModel
	private let coordinator : MSPersistentStoreCoordinator
	private let modelURL : NSURL
	private let dbURL : NSURL
	let context : NSManagedObjectContext

	// MARK: - Initializers
	init?(modelName: String){

		guard let modelURL = NSBundle.mainBundle().URLForResource(modelName,
			withExtension: "momd") else {
				print("Unable to find \(modelName)in the main bundle")
				return nil}
		self.modelURL = model URL

		// Try to create the model from the URL
		guard let model = NSManagedObjectModel(contentsOfURL: modelURL) else{
			print("unable to create a model from \(modelURL)")
		}
		self.model = model

		coordinator = NSPersistentStoreCoordinator(managedObjectModel: model)

		context = NSManagedObjectContext(concurrencyType: .
			MainQueueConcurrencyType)
		context.persistentStoreCoordinator = coordinator

		// Add a SQLite store located in the documents folder
		let fm = NSFileManager.defaultManager()

		guard let docUrl = fm.URLsForDirectory(.DocumentDirectory, inDomains: UserDomainMask).first else {
			print("manage to people the document folder")
			return nil
		}
	}
}

-core data intro
-core data architecture
-create a model, managed objects, and begin our own app

core data
Model(managed objects), View, Controller

Object Model
(aka “managed Object Model”)
-specifies app classes and relationships

Managed Object
-class:NSManagedObject
-example:a character of a game app
-saves the contents of its properties to a DB file

Context
-class:NSManagedObject+Context
-imagine as a place
-where objects live and where operations take place

Fetch request
-searches context for certain managed objects

Fetched Results Controller
-part of controller layer
-controls how data from a fetch request is displayed in a view

Stores
-where managed objects are stored

Store coordinator
-allow you to have multiple stores