Cannot Subscript

Question

For the line of code currentSelection = vendingMachine.selection[indexPath.row] I get an error saying that I cannot subscript a value type of [VendingSelection]. What is going on? Shouldn't it say vendingMachine?

Brian Uribe · Answer

Thank you! I ran into more trouble, i'm starting to think I missed a step somewhere. In the video we move one line of code 
{ if let currrentSelection = currentSelection, let item = vendingMachine.itemForCurrentSelection(currentSelection)
        totalLabel.text = "$(item.price * quantity)"
    }
from one function to another and I suddenly got a ton of errors. I'm feeling a pit overwhelmed.
here is my vending machine code:
//
//  VendingMachine.swift
//  VendingMachine
//
//  Created by Admin on 3/14/16.
//  Copyright © 2016 Treehouse. All rights reserved.
//
import Foundation
import UIKit
// Protocols
protocol VendingMachineType {
    var selection: [VendingSelection] { get }
    var inventory: [VendingSelection: ItemType] { get set }
    var amountDeposited: Double { get set }
init(inventory: [VendingSelection: ItemType])
func vend(selection: VendingSelection, quantity: Double) throws
func deposit(amount: Double)
func itemForCurrentSelection(selection: VendingSelection) -> ItemType?
}
protocol ItemType {
    var price: Double { get }
    var quantity: Double { get set }
}
// Error Types
enum InventoryError: ErrorType {
case InvalidResource
case ConversionError
case InvalidKey
}
enum VendingMachineError: ErrorType {
    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 = NSBundle.mainBundle().pathForResource(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 vendingInventoryFromDictionary(dictionary: [String : AnyObject]) throws -> [VendingSelection : ItemType] {
        var inventory: [VendingSelection : ItemType] = [:]
    for (key, value) in dictionary {
        if let itemDict = value as? [String : Double], let price = itemDict["price"], let quantity = itemDict["quantity"] {

let item = VendingItem(price: price, quantity: quantity)

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

inventory.updateValue(item, forKey: key)
        }

}

return inventory
}
}
// Concrete Types
enum VendingSelection: String {
    case Soda
    case DietSoda
    case Chips
    case Cookie
    case Sandwich
    case Wrap
    case CandyBar
    case PopTart
    case Water
    case FruitJuice
    case SportsDrink
    case Gum
func icon() -> UIImage {
    if let image = UIImage(named: self.rawValue) {
        return image
    } else {
        return UIImage(named: "Default")!
    }

}
}
struct VendingItem: ItemType{
    var price: Double
    var quantity: Double
}
class VendingMachine: VendingMachineType {
    let selection: [VendingSelection] = [.Soda, .DietSoda, .Chips, .Cookie, .Sandwich, .Wrap, .CandyBar, .PopTart, .Water, .FruitJuice, .SportsDrink, .Gum]
    var inventory: [VendingSelection: ItemType]
    var amountDeposited: Double = 10.0
required init(inventory: [VendingSelection : ItemType]) {
self.inventory = inventory
}
func vend(selection: VendingSelection, quantity: Double) throws {
    guard var item = inventory[selection] else {
        throw VendingMachineError.InvalidSelection
    }
guard item.quantity > 0 else {
    throw  VendingMachineError.OutOfStock
}

item.quantity -= quantity
inventory.updateValue(item, forKey: selection)

let totalPrice = item.price * quantity
if amountDeposited >= totalPrice {
    amountDeposited -= totalPrice
} else {
    let amountRequired = totalPrice - amountDeposited
    throw VendingMachineError.InsufficientFunds(required: amountRequired)
}
}
func itemForCurrentSelection(selection: VendingSelection) -> ItemType? {
    return inventory[selection]
}
func deposit(amount: Double) {
    //add code
}
}
and then here is the view controller code:
//
//  ViewController.swift
//  VendingMachine
//
//  Created by Pasan Premaratne on 1/19/16.
//  Copyright © 2016 Treehouse. All rights reserved.
//
import UIKit
private let reuseIdentifier = "vendingItem"
private let screenWidth = UIScreen.mainScreen().bounds.width
class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {
@IBOutlet weak var collectionView: UICollectionView!
@IBOutlet weak var totalLabel: UILabel!
@IBOutlet weak var balanceLabel: UILabel!
@IBOutlet weak var quantityLabel: UILabel!

let vendingMachine: VendingMachineType
var currentSelection: VendingMachine?
var quantity: Double = 1.0

required init?(coder aDecoder: NSCoder) {

do {
        let dictionary = try PlistConverter.dictionaryFromFile("VendingInventory", ofType: "plist")
        let inventory = try InventoryUnarchiver.vendingInventoryFromDictionary(dictionary)
        self.vendingMachine = VendingMachine(inventory: inventory)
    } catch let error {
        fatalError("\(error)")
    }
    super.init(coder: aDecoder)
}

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    setupCollectionViewCells()
    setupViews()
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

func setupViews() {
    updateQuantityLabel()
    updateBalanceLabel()
}

// MARK: - UICollectionView

func setupCollectionViewCells() {
    let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
    layout.sectionInset = UIEdgeInsets(top: 20, left: 0, bottom: 10, right: 0)
    let padding: CGFloat = 10
    layout.itemSize = CGSize(width: (screenWidth / 3) - padding, height: (screenWidth / 3) - padding)
    layout.minimumInteritemSpacing = 10
    layout.minimumLineSpacing = 10

collectionView.collectionViewLayout = layout
}

func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return vendingMachine.selection.count
}

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCellWithReuseIdentifier(reuseIdentifier, forIndexPath: indexPath) as! VendingItemCell

let item = vendingMachine.selection[indexPath.row]
    cell.iconView.image = item.icon()

return cell
}

func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
    updateCellBackgroundColor(indexPath, selected: true)
    reset()
    currentSelection = vendingMachine.selection[indexPath.row]
    updateTotalPrice()

func collectionView(collectionView: UICollectionView, didDeselectItemAtIndexPath indexPath: NSIndexPath) {
    updateCellBackgroundColor(indexPath, selected: false)
}

func collectionView(collectionView: UICollectionView, didHighlightItemAtIndexPath indexPath: NSIndexPath) {
    updateCellBackgroundColor(indexPath, selected: true)
}

func collectionView(collectionView: UICollectionView, didUnhighlightItemAtIndexPath indexPath: NSIndexPath) {
    updateCellBackgroundColor(indexPath, selected: false)
}

func updateCellBackgroundColor(indexPath: NSIndexPath, selected: Bool) {
    if let cell = collectionView.cellForItemAtIndexPath(indexPath) {
        cell.contentView.backgroundColor = selected ? UIColor(red: 41/255.0, green: 211/255.0, blue: 241/255.0, alpha: 1.0) : UIColor.clearColor()
    }
}

// MARK: - Helper Methods
@IBAction func purchase() {
    if let currentSelection = currentSelection {
        do {
            try vendingMachine.vend(currentSelection, quantity: quantity)
           updateBalanceLabel()
        } catch {
            //FIXME: Error Handling Code
        }
    } else {
        // FIXME: Alert user to no selection
    }

}

@IBAction func updateQuantity(sender: UIStepper) {
    quantity = sender.value
    updateTotalPriceLabel()
    updateQuantityLabel()
}

func updateTotalPrice () { if let currrentSelection = currentSelection, let item = vendingMachine.itemForCurrentSelection(currentSelection)
    totalLabel.text = "$\(item.price * quantity)"
}
}

func updateQuantityLabel() {
    quantityLabel.text = "\(quantity)"
}

func updateBalanceLabel() {
    balanceLabel.text = "$\(vendingMachine.amountDeposited)"

}

func reset() {
    quantity = 1
    updateTotalPriceLabel()
    updateQuantityLabel()
}
}

Steven Deutsch · Answer

Hey Brian Uribe,
I'm thinking that you have your currentSelection variable set to the wrong type. You might have it as [VendingSelection] when it needs to be of type VendingSelection.
This is how it should read:
Swift
  var currentSelection: VendingSelection?
`
Let me know if this helps. If not, please show me your view controller code.
Your VendingMachine.swift file would also be helpful.
Thanks

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Brian Uribe

Brian Uribe

Cannot Subscript

2 Answers

Steven Deutsch

Steven Deutsch

Brian Uribe

Brian Uribe

Brian Uribe

Brian Uribe

Steven Deutsch

Steven Deutsch