swift 之xib自定义view可视化到storyboard

@IBDesignable
class IDCard: UIView {
    
    @IBOutlet var contentView: UIView!
    

    @IBInspectable
    var cornerRadius: CGFloat = 0 {
        didSet {
            layer.cornerRadius = cornerRadius
            layer.masksToBounds = cornerRadius > 0
        }
    }
    @IBInspectable
    var borderWidth: CGFloat = 0 {
        didSet {
            layer.borderWidth = borderWidth
        }
    }
    @IBInspectable
    var borderColor: UIColor? {
        didSet {
            layer.borderColor = borderColor?.CGColor
        }
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        initialFromXib()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        initialFromXib()
    }
    
    func initialFromXib() {
        let bundle = NSBundle(forClass: self.dynamicType)
        let nib = UINib(nibName: "IDCard", bundle: bundle)
        contentView = nib.instantiateWithOwner(self, options: nil)[0] as! UIView
        contentView.frame = bounds
        addSubview(contentView)
        
    }
    
}