Integrate Combine Into an App

Aug 5 2021 · Swift 5.4, macOS 11.3, Xcode 12.5

Part 2: Integrate with Core Data & Unit Test

06. Extend, Save & Delete Core Data Objects

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Previous episode: Part 1 Quiz: Integrate Combine into an App Next episode: 07. Create the Core Data Stack

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Earlier when we defined places we could use Combine in our Jokes app, we determined that fetching a list of saved jokes would be a great piece of functionality to show off the powers of Combine - but we need to have data in the database before we can do that!

import Foundation
import SwiftUI
import CoreData
import ChuckNorrisJokesModel

extension JokeManagedObject {

  static func save(joke: Joke, inViewContext viewContext: NSManagedObjectContext) {
    guard != "error" else { return }
    let fetchRequest = NSFetchRequest<NSFetchRequestResult>(
      entityName: String(describing: JokeManagedObject.self))
    fetchRequest.predicate = NSPredicate(format: "id = %@",
    if let results = try? viewContext.fetch(fetchRequest),
       let existing = results.first as? JokeManagedObject {
      existing.value = joke.value
      existing.categories = joke.categories as NSArray
      existing.languageCode = joke.languageCode
      existing.translationLanguageCode = joke.translationLanguageCode
      existing.translatedValue = joke.translatedValue
    } else {
      let newJoke = self.init(context: viewContext) =
      newJoke.value = joke.value
      newJoke.categories = joke.categories as NSArray
      newJoke.languageCode = joke.languageCode
      newJoke.translationLanguageCode = joke.translationLanguageCode
      newJoke.translatedValue = joke.translatedValue
    do {
    } catch {
      fatalError("\(#file), \(#function), \(error.localizedDescription)")

extension Collection where Element == JokeManagedObject, Index == Int {
  // 1
  func delete(at indices: IndexSet, inViewContext viewContext: NSManagedObjectContext) {
    // 2
    indices.forEach { index in
    // 3
    do {
    } catch {
      fatalError("\(#file), \(#function), \(error.localizedDescription)")