Пример класса

import UIKit

@IBDesignable class UIViewDes: UIView {
    @IBInspectable var borderColor: UIColor = UIColor.clear{
        didSet{
            layer.borderColor = borderColor.cgColor
        }
    }
    @IBInspectable var borderWidth:CGFloat = 1 {
        didSet{
            layer.borderWidth = borderWidth
        }
    }
    
    @IBInspectable var corderRadius: CGFloat = 0 {
        didSet{
            layer.cornerRadius = corderRadius
        }
    }
    
    override func awakeFromNib() {
        super.awakeFromNib()
    }
}

Полезный сайт