CoreData.swift

private func saveSomeArticles() {
        guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
            return
        }

        // 1
        let context = appDelegate.persistentContainer.viewContext

        // 2
        let mediumArticle = Article(context: context)

        // 3
        mediumArticle.title = randomString(length: 10)
        mediumArticle.content = randomString(length: 50)

        // 4
        appDelegate.saveContext()
    }