CoreDataManager cheatsheet

CoreDataManager.swift

import CoreData
import UIKit

// ./NoteList.xcdatamodeld

class CoreDataManager {
  static let sharedInstance = CoreDataManager()
  
  private init() { }
  
  lazy var persistentContainer: NSPersistentContainer = {
      let container = NSPersistentContainer(name: "NoteList")
      container.loadPersistentStores(completionHandler: { (storeDescription, error) in
          if let error = error as NSError? {
              fatalError("Unresolved error \(error), \(error.userInfo)")
          }
      })
      return container
  }()
  
  func fetchAllNotes() -> [Note] {
    let fetchRequest: NSFetchRequest<Note> = Note.fetchRequest()
    let context = persistentContainer.viewContext
    guard let results = try? context.fetch(fetchRequest) else {
      return []
    }
    
    return results
  }
  
  func createNote(for title: String, content: String) {
    let managedObjectContext = persistentContainer.viewContext
    let note = Note(context: managedObjectContext)
    note.title = title
    note.content = content
    note.createdDate = Date()
    note.id = UUID()
    
    do {
      try managedObjectContext.save()
    } catch {
      print(error)
    }
  }
  
  func fetchNote(for id: UUID) -> Note? {
    let predicate = NSPredicate(format: "id == %@", id as CVarArg)
    let fetchRequest: NSFetchRequest<Note> = Note.fetchRequest()
    fetchRequest.predicate = predicate
    let context = persistentContainer.viewContext
    
    guard let results = try? context.fetch(fetchRequest) else {
      return nil
    }
    
    return results.first
  }
  
  func delete(for noteId: UUID) {
    guard let note = fetchNote(for: noteId) else {
      return
    }
    
    let context = persistentContainer.viewContext
    
    do {
      context.delete(note)
      try context.save()
    } catch {
      print("Error saving: \(error)")
    }
  }
}