ObjectTemplate.swift

class Product {
    var name:String
    var price:Double
    private var stockBackingValue:Int = 0
    
    var stock:Int {
        get {
            return stockBackingValue
        }
        set {
            stockBackingValue = max(0, newValue)
        }
    }
    
    init(name:String, price:Double, stock:Int) {
        self.name = name
        self.price = price
        self.stock = stock
    }
    
    func calculateTax(rate: Double) -> Double {
        return min(10, self.price * rate)
    }
    
    var stockValue: Double {
        get {
            return self.price * Double(self.stock)
        }
    }
}
let product = Product(name: "hoge", price: 1000.0, stock: 200)
product.stockValue