Decorator.swift

class Purchase : CustomStringConvertible {
    private let product:String
    private let price:Float
    
    init(product:String, price:Float) {
        self.product = product
        self.price = price
    }
    
    var description:String {
        return product
    }
    
    var totalPrice:Float {
        return price
    }
}

class CustomAccount {
    let customName:String
    var purchases = [Purchase]()
    
    init(name:String) {
        self.customName = name
    }
    
    func addPurchase(purchase:Purchase) {
        self.purchases.append(purchase)
    }
    
    func printAccount() {
        var total:Float = 0
        for p in purchases {
            total += p.totalPrice
            print("Purchase \(p), Price " +
            "\(formatCurrencyString(p.totalPrice))")
        }
        print("Total due: \(formatCurrencyString(total))")
    }
    
    func formatCurrencyString(number:Float) -> String {
        let formatter = NSNumberFormatter()
        formatter.numberStyle = NSNumberFormatterStyle.CurrencyStyle
        formatter.locale = NSLocale(localeIdentifier: "en_US")
        return formatter.stringFromNumber(number) ?? ""
    }
}

let account = CustomAccount(name: "Joe")
account.addPurchase(Purchase(product: "Red Hat", price: 10))
account.addPurchase(Purchase(product: "Scarf", price: 20))
account.printAccount()