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iOS Build a Vending Machine App in Swift Using the Vending Machine Testing Out the Vending Machine

Gavin Hobbs
Gavin Hobbs
5,205 Points

Use of unresolved identifier 'quantity'

I'm getting the error Use of unresolved identifier 'quantity' and I can't figure out what I'm doing wrong. Any help would be greatly appreciated!

ViewController.swift

//
//  ViewController.swift
//  VendingMachine
//
//  Created by Pasan Premaratne on 12/1/16.
//  Copyright © 2016 Treehouse Island, Inc. All rights reserved.
//

import UIKit

fileprivate let reuseIdentifier = "vendingItem"
fileprivate let screenWidth = UIScreen.main.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!
    @IBOutlet weak var priceLabel: UILabel!

    let vendingMachine: VendingMachine
    var currentSelection: VendingSelection?

    required init?(coder aDecoder: NSCoder) {
        do {
            let dictionary = try PlistConverter.dictionary(fromFile: "VendingInventory", ofType: "plist")
            let inventory = try InventoryUnarchiver.vendingInvetory(fromDictionary: dictionary)
            self.vendingMachine = FoodVendingMachine(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()
        print(vendingMachine.inventory)
    }

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

    // MARK: - Setup

    func setupCollectionViewCells() {
        let layout = UICollectionViewFlowLayout()
        layout.sectionInset = UIEdgeInsets(top: 0, left: 0, bottom: 20, right: 0)

        let padding: CGFloat = 10
        let itemWidth = screenWidth/3 - padding
        let itemHeight = screenWidth/3 - padding

        layout.itemSize = CGSize(width: itemWidth, height: itemHeight)
        layout.minimumLineSpacing = 10
        layout.minimumInteritemSpacing = 10

        collectionView.collectionViewLayout = layout
    }

    // MARK: - Vending Machine

    @IBAction func purchase() {
        if let currentSelection = currentSelection {
            do {
                try vendingMachine.vend(selection: currentSelection, quantity: quantity)
            } catch {
                // FIXME: Error handling code
            }
        } else {
            // FIXME: Alert user to no selection

        }
    }


    // MARK: UICollectionViewDataSource

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

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath) as? VendingItemCell else { fatalError() }

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

        return cell
    }

    // MARK: - UICollectionViewDelegate

    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        updateCell(having: indexPath, selected: true)

        currentSelection = vendingMachine.selection[indexPath.row]

        if let currentSlection = currentSelection, let item = vendingMachine.item(forSelection: currentSelection) {
            priceLabel.text = "$\(item.price)"
            totalLabel.text = "$\(item.price * Double(quantity))"
        }
    }

    func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
        updateCell(having: indexPath, selected: false)
    }

    func collectionView(_ collectionView: UICollectionView, didHighlightItemAt indexPath: IndexPath) {
        updateCell(having: indexPath, selected: true)
    }

    func collectionView(_ collectionView: UICollectionView, didUnhighlightItemAt indexPath: IndexPath) {
        updateCell(having: indexPath, selected: false)
    }

    func updateCell(having indexPath: IndexPath, selected: Bool) {

        let selectedBackgroundColor = UIColor(red: 41/255.0, green: 211/255.0, blue: 241/255.0, alpha: 1.0)
        let defaultBackgroundColor = UIColor(red: 27/255.0, green: 32/255.0, blue: 36/255.0, alpha: 1.0)

        if let cell = collectionView.cellForItem(at: indexPath) {
            cell.contentView.backgroundColor = selected ? selectedBackgroundColor : defaultBackgroundColor
        }
    }


}

VendingMachine.swift

//
//  VendingMachine.swift
//  VendingMachine
//
//  Created by Gavin Hobbs on 11/1/17.
//  Copyright © 2017 Treehouse Island, Inc. All rights reserved.
//

import Foundation
import UIKit


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 #imageLiteral(resourceName: "default")
        }
    }
}

protocol VendingItem {
    var price: Double { get }
    var quantity: Int { get set }
}

protocol VendingMachine {
    var selection: [VendingSelection] { get }
    var inventory: [VendingSelection: VendingItem] { get set }
    var amountDeposited: Double { get set }

    init(inventory: [VendingSelection: VendingItem])

    func vend(selection: VendingSelection, quantity: Int) throws
    func deposit(_ amount: Double)
    func item(forSelection selection: VendingSelection) -> VendingItem?
}

struct Item: VendingItem {
    let price: Double
    var quantity: Int
}

enum InventoryError: Error {
    case invalidResource
    case conversionFailure
    case invalidSelection
}

class PlistConverter {
    static func dictionary(fromFile name: String, ofType type: String) throws -> [String: AnyObject] {
        guard let path = Bundle.main.path(forResource: name, ofType: type) else {
            throw InventoryError.invalidResource
        }

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

        return dictionary
    }
}

class InventoryUnarchiver {
    static func vendingInvetory(fromDictionary dictionary: [String: AnyObject]) throws -> [VendingSelection: VendingItem] {

        var inventory: [VendingSelection: VendingItem] = [:]

        for (key, value) in dictionary {
            if let itemDictionary = value as? [String: Any], let price = itemDictionary["price"] as? Double, let quantity = itemDictionary["quantity"] as? Int {
                let item = Item(price: price, quantity: quantity)

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

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

        return inventory
    }
}

enum VendingMachineError: Error {
    case invalidSelection
    case outOfStock
    case insufficientFunds(required: Double)
}

class FoodVendingMachine: VendingMachine {
    let selection: [VendingSelection] = [.soda, .dietSoda, .chips, .sandwich, .wrap, .candyBar, .popTart, .water, .fruitJuice, .sportsDrink, .gum]
    var inventory: [VendingSelection : VendingItem]
    var amountDeposited: Double = 10.0

    required init(inventory: [VendingSelection : VendingItem]) {
        self.inventory = inventory
    }

    func vend(selection: VendingSelection, quantity: Int) throws {
        guard var item = inventory[selection] else {
            throw VendingMachineError.invalidSelection
        }

        guard item.quantity >= quantity else {
            throw VendingMachineError.outOfStock
        }

        let totalPrice = item.price * Double(quantity)

        if amountDeposited >= totalPrice {
            amountDeposited -= totalPrice

            item.quantity -= quantity

            inventory.updateValue(item, forKey: selection)
        } else {
            let amountRequired = totalPrice - amountDeposited
            throw VendingMachineError.insufficientFunds(required: amountRequired)
        }
    }

    func deposit(_ amount: Double) {

    }

    func item(forSelection selection: VendingSelection) -> VendingItem? {
        return inventory[selection]
    }
}

Thanks!

  • Gavin

1 Answer

After var currentSelection: VendingSelection? in the View Controller, You should create a variable named quantity and set it equal to 1 as the initial value

Hope that helps :)

Gavin Hobbs
Gavin Hobbs
5,205 Points

Thanks Josh Byron ! Sometimes it's the smallest mistakes that are the most confusing! :p