Saving state of the Pokedex - ios

Question

My goal is to write a code such that If I stop running the app and then run it again, the Pokédex will remember which Pokémon are caught and which aren’t by saving that state to disk. I wrote some code but I'm getting an error "Thread 1: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value" at "if UserDefaults.standard.bool(forKey: self.pokemon.name) {" line of the code.
Here's my code,
PokemonViewController
import UIKit
class PokemonViewController: UIViewController {
var url: String!
var caught = false
var pokemon: PokemonListResult!
#IBOutlet var nameLabel: UILabel!
#IBOutlet var numberLabel: UILabel!
#IBOutlet var type1Label: UILabel!
#IBOutlet var type2Label: UILabel!
#IBOutlet var catchButton: UIButton!
func capitalize(text: String) -> String {
return text.prefix(1).uppercased() + text.dropFirst()
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
nameLabel.text = ""
numberLabel.text = ""
type1Label.text = ""
type2Label.text = ""
loadPokemon()
}
func loadPokemon() {
URLSession.shared.dataTask(with: URL(string: url)!) { (data, response, error) in
guard let data = data else {
return
}
do {
let result = try JSONDecoder().decode(PokemonResult.self, from: data)
DispatchQueue.main.async {
self.navigationItem.title = self.capitalize(text: result.name)
self.nameLabel.text = self.capitalize(text: result.name)
self.numberLabel.text = String(format: "#%03d", result.id)
if UserDefaults.standard.bool(forKey: self.pokemon.name) {
self.caught = true
self.catchButton.setTitle("Release", for: [])
} else {
self.caught = false
self.catchButton.setTitle("Catch", for: [])
}
for typeEntry in result.types {
if typeEntry.slot == 1 {
self.type1Label.text = typeEntry.type.name
}
else if typeEntry.slot == 2 {
self.type2Label.text = typeEntry.type.name
}
}
}
}
catch let error {
print(error)
}
}.resume()
}
#IBAction func toggleCatch() {
caught = !caught
UserDefaults.standard.set(caught, forKey: pokemon.name)
if UserDefaults.standard.bool(forKey: pokemon.name) {
catchButton.setTitle("Release", for: [])
} else {
catchButton.setTitle("Catch", for: [])
}
}
}
Pokemon
import Foundation
struct PokemonListResults: Codable {
let results: [PokemonListResult]
}
struct PokemonListResult: Codable {
let name: String
let url: String
}
struct PokemonResult: Codable {
let id: Int
let name: String
let types: [PokemonTypeEntry]
}
struct PokemonTypeEntry: Codable {
let slot: Int
let type: PokemonType
}
struct PokemonType: Codable {
let name: String
}

Answer 1

Your instance variable pokemon is an implicitly unwrapped optional.
This line:
var pokemon: PokemonListResult!
If you try to reference the variable pokemon before storing a value there, you will get exactly the crash you describe. Your code is trying to read a value from pokemon and it's nil. (self.pokemon.name). Don't do that.
(The code you posted never puts a value into your pokemon instance variable.)