UIView.move(_:to) concept - a thought about a what a 'swifty' api might look like

UIView+move.swift

public enum ViewIndex {
    case front, back
    case index(Int)
    case above(UIView)
    case below(UIView)
}
private extension ViewIndex {
    private func indexOfView(view: UIView, in parent: UIView) throws -> Int {
        guard let index = parent.subviews.index(of: view) else { throw ViewIndexError.viewNotInHierarchy(view) }
        return index
    }
    func indexIn(parent: UIView) throws -> Int {
        switch self {
        case .back: return 0
        case .front: return parent.subviews.count
        case .index(let value): return value
        case .above(let target): return try self.indexOfView(view: target, in: parent).advanced(by: 1)
        case .below(let target): return try self.indexOfView(view: target, in: parent).advanced(by: -1)
        }
    }
}
public enum ViewIndexError: Error {
    case viewNotInHierarchy(UIView)
}
public extension UIView {
    public func move(_ view: UIView, to index: ViewIndex) throws {
        view.removeFromSuperview()
        self.insertSubview(view, at: try index.indexIn(parent: self))
    }
}