Photo by Gunnar Ridderström on Unsplash

圖4-5

// 程式列 4-12

class Utils {
    class func currencyStringFromNumber(number: Double) -> String {
        // MARK: 'NSNumberFormatter' has been renamed to 'NumberFormatter'
        let formatter = NumberFormatter();
        formatter.numberStyle = .currency;
        return formatter.string(from: NSNumber(value: number)) ?? "";
    }
}

more

認識Swift Access Control

• https://www.swiftbysundell.com/basics/access-control/
• https://www.appcoda.com/swift-access-levels/
• https://stackoverflow.com/questions/39027250/what-is-a-good-example-to-differentiate-between-fileprivate-and-private-in-swift/41261058#41261058

// 程式列 4-14

import UIKit

class ProductTableCell: UITableViewCell {
    @IBOutlet weak var nameLabel: UILabel!
    @IBOutlet weak var descriptionLabel: UILabel!
    @IBOutlet weak var stockStepper: UIStepper!
    @IBOutlet weak var stockField: UITextField!

    var product: Product?
}

class ViewController: UIViewController, UITableViewDataSource {
    @IBOutlet weak var totalStockLabel: UILabel!
    @IBOutlet weak var tableView: UITableView!

    var products = [
        Product(name: "Kayak", description: "A boat for one person",
                category: "Watersports", price: 275.0, stockLevel: 10),
        Product(name: "Lifejacket", description: "Protective and fashionable",
                category: "Watersports", price: 48.95, stockLevel: 14),
        Product(name: "Soccer Ball", description: "FIFA-approved size and weight",
                category: "Soccer", price: 19.5, stockLevel: 32),
        Product(name: "Corner Flags",
                description: "Give your playing field a professional touch",
                category: "Soccer", price: 34.95, stockLevel: 1),
        Product(name: "Stadium", description: "Flat-packed 35,000-seat stadium",
                category: "Soccer", price: 79500.0, stockLevel: 4),
        Product(name: "Thinking Cap",
                description: "Improve your brain efficiency by 75%",
                category: "Chess", price: 16.0, stockLevel: 8),
        Product(name: "Unsteady Chair",
                description: "Secretly give your opponent a disadvantage",
                category: "Chess", price: 29.95, stockLevel: 3),
        Product(name: "Human Chess Board",
                description: "A fun game for the family", category: "Chess",
                price: 75.0, stockLevel: 2),
        Product(name: "Bling-Bling King",
                description: "Gold-plated, diamond-studded King",
                category: "Chess", price: 1200.0, stockLevel: 4)]

    override func viewDidLoad() {
        super.viewDidLoad()
        displayStockTotal()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return products.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let product = products[indexPath.row]
        let cell = tableView.dequeueReusableCell(withIdentifier: "ProductCell") as! ProductTableCell
        cell.product = products[indexPath.row]
        cell.nameLabel.text = product.name
        cell.descriptionLabel.text = product.description
        cell.stockStepper.value = Double(product.stockLevel)
        cell.stockField.text = String(product.stockLevel)
        return cell
    }

    @IBAction func stockLevelDidChange(_ sender: AnyObject) {
        if var currentCell = sender as? UIView {
            while true {
                currentCell = currentCell.superview!
                if let cell = currentCell as? ProductTableCell {
                    // MARK: Remove ?
                    if let product = cell.product {
                        if let stepper = sender as? UIStepper {
                            product.stockLevel = Int(stepper.value)
                        } else if let textfield = sender as? UITextField {
                            // MARK: In Swift 2.x, the .toInt() function was removed from String.
                            if let newValue = Int(textfield.text!) {
                                product.stockLevel = newValue
                            }
                        }

                        cell.stockStepper.value = Double(product.stockLevel)
                        cell.stockField.text = String(product.stockLevel)
                    }
                    break
                }
            }
            displayStockTotal()
        }
    }
    func displayStockTotal() {
        let stockTotal = products.reduce(0, {(total, product) -> Int in return total + product.stockLevel})
        totalStockLabel.text = "\(stockTotal) Products in Stock"
    }

}

// 程式列 4-15

    func displayStockTotal() {
        let finalTotals: (Int, Double) = products.reduce((0, 0.0),
        {(totals, product) -> (Int, Double) in
            return (
                totals.0 + product.stockLevel,
                totals.1 + product.stockValue
            );
        });
        
        totalStockLabel.text = "\(finalTotals.0) Products in Stock. " + "Total Values: \(Utils.currencyStringFromNumber(number: finalTotals.1))"
    }

結尾
今天週一症候群表示：

謝謝閱讀～