// Assuming .xib name is the same as class name

extension UIView {
    func nibView<T>(for: T.Type) -> UIView? {
        let nib = UINib(nibName: String(describing: T.self), bundle: nil)
        let view = nib.instantiate(withOwner: self, options: nil).first as? UIView
        return view
    }

    func addNibView<T>(from: T.Type) -> UIView? {
        guard let nibView = nibView(for: T.self) else{ return nil }
        addSubview(nibView)
        nibView.frame = bounds
        return nibView
    }
}

// To Use

class CustomView: UIView {

    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        commonInit()
    }

    private func commonInit() {
        guard let view = addNibView(from: CustomView.self) else { return }
        // Do stuff with view
        // view.layer.cornerRadius = Constants.PRIMARY_CORNER_RADIUS
    }

}