example for convenience init with let initialization

class CustomLabel: UILabel {

    let edgeInsets: UIEdgeInsets

    init(frame: CGRect, insets: UIEdgeInsets) {
        edgeInsets = insets
        super.init(frame: frame)
    }

    convenience init(text: String?, dx: CGFloat, dy: CGFloat) {
        let insets = UIEdgeInsets(top: dy, left: dx, bottom: dy, right: dx)
        self.init(frame: .zero, insets: insets)
    }
    }