xib可视化自定义变量

@IBInspectable 让类的支持kvo的属性可以在Xib里面进行设置

@IBDesignable 让xib里面的设置立即可见
范例

@IBDesignable class PanaStackView: UIView {    @IBInspectable var cornerRa:CGFloat{        set{            self.layer.cornerRadius = newValue        }        get{            return self.layer.cornerRadius        }    }}