Swift 4.2“错误”方法失败，原因：对象中的键无效。为什么？

Question

在Swift 4.2中，“错误”方法失败，并显示错误：对象中的键无效。更改项目名称后，它给出了错误。代码是：

GreenGrocer.swift：

import UIKit

private let reuseIdentifier = "grocerItem"
private let screenWidth = UIScreen.main.bounds.width

class ViewController: UIViewController, UICollectionViewDataSource, 
UICollectionViewDelegate {

@IBOutlet weak var quantityStepper: UIStepper!
@IBOutlet weak var collectionView: UICollectionView!
@IBOutlet weak var totalLabel: UILabel!
@IBOutlet weak var balanceLabel: UILabel!
@IBOutlet weak var quantityLabel: UILabel!

let greenGrocer: GreenGrocerType
var currentSelection: GrocerSelection?
var quantity: Double = 2.0


required init?(coder aDecoder: NSCoder) {
 do {
  // decoupled
    let dictionary = try PlistConverter.dictionaryFromFile(resource: 
"GrocerInventory", ofType: "plist")
    let inventory = try 
InventoryUnarchiver.grocerInventoryFromDictionary(dictionary: 
dictionary)
   self.greenGrocer = GreenGrocer(inventory: inventory)
} catch let error {
    fatalError("\(error)")
}

super.init(coder: aDecoder)
}

override func viewDidLoad() {
super.viewDidLoad()
setupCollectionViewCells()
setupViews()
}

可能是由于项目图标名称的更改或类似原因而失败。 ViewController.swift：

import Foundation
import UIKit

// requirements
protocol GreenGrocerType {
var selection: [GrocerSelection] { get }
var inventory: [GrocerSelection: ItemType] { get set }
var amountDeposited: Double { get set }

init(inventory: [GrocerSelection: ItemType])

func grocer(selection: GrocerSelection, quantity: Double) throws
func itemForCurrentSelection(selection: GrocerSelection) -> ItemType?
func deposit(amount: Double)
}

protocol ItemType {
var price: Double { get }
var quantity: Double { get set }
}


// error types
enum   InventoryError: Error {
case InvalidResource
case ConversionError
case InvalidKey
}

enum   GrocerError: Error {
case InvalidSelection
case OutOfStock
case InsufficientFunds(required: Double)
}

// helper classes
class PlistConverter {
class func dictionaryFromFile(resource: String, ofType type:String) 
throws -> [String: AnyObject] {
guard let path = Bundle.main.path(forResource: resource, ofType: type) 
else {
  throw InventoryError.InvalidResource
 }

 guard let dictionary = NSDictionary(contentsOfFile: path), let 
 castDictionary = dictionary as? [String: AnyObject] else {
  throw InventoryError.ConversionError
 }

 return castDictionary
 }
}

class InventoryUnarchiver {
class func grocerInventoryFromDictionary(dictionary: [String: 
AnyObject]) throws -> [GrocerSelection: ItemType] {
var inventory: [GrocerSelection: ItemType] = [:]

 for (key, val) in dictionary {
  if let itemDict = val as? [String: Double], let price = 
 itemDict["price"], let quantity = itemDict["quantity"] {
    let item = GrocerItem(price: price, quantity: quantity)

    guard let key = GrocerSelection(rawValue: key) else {
      throw InventoryError.InvalidKey
    }

    inventory.updateValue(item, forKey: key)
   }
  }

 return inventory
 }
}

我什么都没找到，或者我误会了什么？