Error when try to unwrap realm object - ios

Question

I have following issue when I try to use data from one of Realm Objects
I have an error:
Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value
I'm confused because when I try to do it manually on debug console all works fine
(lldb) print meal?.mealName
(String?) $R0 = "Krem buraczany"
I will attach whole code and show you on which line error appear
Realm Object:
import UIKit
import RealmSwift
class Meal: Object {
#objc dynamic var mealID : String = ""
#objc dynamic var mealName : String = ""
var ingredients = List<String>()
var mealDescription = List<String>()
#objc dynamic var kcal : Int = 0
#objc dynamic var preparingTime : Int = 0
#objc dynamic var imageName : String = ""
convenience init(mealID: String, mealName: String, kcal: Int, preparingTime: Int, imageName: String) {
self.init()
self.mealID = mealID
self.mealName = mealName
self.kcal = kcal
self.preparingTime = preparingTime
self.imageName = imageName
}
override static func primaryKey() -> String? {
return "mealID"
}
}
Sending data via segue:
#IBAction func ideaForMealButtonPressed(_ sender: UIButton) {
performSegue(withIdentifier: "ideaForMeal", sender: self)
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
let destinationVC = segue.destination as! IdeaForMeal
destinationVC.randomMeal = getRandomMeal()
}
func getRandomMeal() -> String {
var mealsCount = realm.objects(Meal.self).count
mealsCount += 1
let randomMealID = arc4random_uniform(UInt32(mealsCount))
print (randomMealID)
return String(randomMealID)
}
Receiver:
//Global Variables
let realm = try! Realm()
var randomMeal : String? {
didSet {
let selectedMeal = downloadMealData(mealID: randomMeal!)
setUIForMeal(meal: selectedMeal)
}
}
override func viewDidLoad() {
super.viewDidLoad()
self.hideKeyboardWhenTappedAround()
}
//Background Operations
func downloadMealData(mealID: String?) -> Meal? {
let currentMeal = realm.object(ofType: Meal.self, forPrimaryKey: mealID)
return currentMeal
}
func checkPositionOfTopIngredientsLabel() -> CGFloat {
let maxY = ingredientsTopLabel.frame.maxY
return maxY
}
func setUIForMeal(meal: Meal?) {
mealNameLabel.text = meal!.mealName // Error!
mealImage.image = UIImage(named: meal!.imageName)
preparingTimeLabel.text = String(meal!.preparingTime)
kcalLabel.text = String(meal!.kcal)
}
Thanks!
BR
iMat

Answer 1

The error is not related to Realm. It's a very common view life cycle mistake.
Setting randomMeal in the destination view controller triggers the didSet observer. The observer is going to access an IBOutlet which is not connected yet.
A solution is to run the code in viewDidLoad
var randomMeal = ""
override func viewDidLoad() {
super.viewDidLoad()
self.hideKeyboardWhenTappedAround()
if !randomMeal.isEmpty {
let selectedMeal = downloadMealData(mealID: randomMeal)
setUIForMeal(meal: selectedMeal)
}
}