创建模板类（封装一个类）
例1:
新建一个名字叫做 Product 的类
Product.swift File 的内容
class Product { var name: String var description: String var price: Double var stock: Int init(name: String, description: String, price: Double, stock: Int) { self.name = name self.description = description self.price = price self.stock = stock } }
例2:
override func viewDidLoad() {
super.viewDidLoad()
let circle = CircleView(frame: CGRectMake(100, 150, 150, 150))
self.view.addSubview(circle)
self.addLabel(circle1.frame, text: "X", fontSize: 60)
}
func addLabel(frame: CGRect, text: String, fontSize: CGFloat) {
let label = UILabel(frame: frame)
label.text = text
label.textAlignment = .Center
label.font = UIFont.systemFontOfSize(fontSize, weight: 10)
self.view.addSubview(label)
}