Incorrect example for Yandex iOS course `Создаёте заметку, копируете ее, меняете поле цвета в одной очереди асинхронно, из другой очереди читаете/пишете цвет из копии заметки`

Note.playground

import Foundation
import UIKit

struct Note {
    
    enum Importance: UInt {
        case unimportant = 0, normal, important
    }
    
    let uid: String
    var title: String
    var content: String
    var color: UIColor
    var importance: Importance
    var selfDestructDate: Date?
    
    init(uid: String = UUID().uuidString, title: String, content: String, color: UIColor = .white, importance: Importance, destructDate: Date? = nil) {
        
        self.uid = uid
        self.title = title
        self.content = content
        self.importance = importance
        self.color = color
        selfDestructDate = destructDate
    }
}

var a = Note(title: "Note 1", content: "Text 1", importance: .normal)
var b = a


DispatchQueue.global().async {
    a.color = .red
    a.title = "Note changed 1"
    a.content = "Text changed 1"
    a.importance = .important
    a.selfDestructDate = Date()
    
    DispatchQueue.main.async {
        sleep(2)
        print(">> a \(a)")
    }
}


DispatchQueue.global(qos: .utility).async {
    sleep(3)
    print(">> utility: b \(b)")
}

DispatchQueue.global(qos: .background).async {
    print(">> background: b \(b)")
}

OUTPUT

>> background: b Note(uid: "21F1387A-A815-46D7-AB45-BFF30FCC465E", title: "Note 1", content: "Text 1", color: UIExtendedGrayColorSpace 1 1, importance: __lldb_expr_11.Note.Importance.normal, selfDestructDate: nil)
>> a Note(uid: "21F1387A-A815-46D7-AB45-BFF30FCC465E", title: "Note changed 1", content: "Text changed 1", color: UIExtendedSRGBColorSpace 1 0 0 1, importance: __lldb_expr_11.Note.Importance.important, selfDestructDate: Optional(2019-08-07 18:08:59 +0000))
>> utility: b Note(uid: "21F1387A-A815-46D7-AB45-BFF30FCC465E", title: "Note 1", content: "Text 1", color: UIExtendedGrayColorSpace 1 1, importance: __lldb_expr_11.Note.Importance.normal, selfDestructDate: nil)