[UIKit] Exercise - UIStepper

#11 瘋狂購物 App — UIStepper 和數字變字串練習

做法：

UIStepper拉Outlet，用來獲取Stepper裡的value (counting)

@IBOutlet weak var labelCheckout: UILabel!
@IBOutlet weak var stepper1: UIStepper!
@IBOutlet weak var stepper2: UIStepper!
@IBOutlet weak var stepper3: UIStepper!

做了幾個Label，用來顯示Stepper裡的value (counting)

@IBOutlet weak var book1QuanityLabel: UILabel!
@IBOutlet weak var book2QuanityLabel: UILabel!
@IBOutlet weak var book3QuanityLabel: UILabel!

設定商品價格，用來計算總價

let book1Price = 6.88
let book2Price = 7.22
let book3Price = 3.99

func，分別計算商品的價格乘數量，加總，顯示到Label

func updateCart(){
    let book1Total = book1Price * stepper1.value
    let book2Total = book2Price * stepper2.value
    let book3Total = book3Price * stepper3.value
    let allBookTotal = String(format: "%.2f", book1Total + book2Total + book3Total)
    labelCheckout.text = "Checkout: $\(allBookTotal)"
}

func，顯示Stepper裡的value到相應商品的label

func updateQuanityLabels(){
    book1QuanityLabel.text = "Quanity: \(Int(stepper1.value))"
    book2QuanityLabel.text = "Quanity: \(Int(stepper2.value))"
    book3QuanityLabel.text = "Quanity: \(Int(stepper3.value))"
}

把幾個Stepper拉Action，在每個Action裡call寫好的兩個func來update Label Text

@IBAction func book1Count(_ sender: Any) {
   updateCart()
   updateQuanityLabels()
}
@IBAction func book2Count(_ sender: Any) {
   updateCart()
   updateQuanityLabels()
}
@IBAction func book3Count(_ sender: Any) {
   updateCart()
   updateQuanityLabels()
}