Instance Method
url(relativeTo:)
iOS 8.0+
iPadOS 8.0+
Mac Catalyst 8.0+
macOS 10.10+
tvOS 9.0+
watchOS 2.0+
Returns a URL based on the components relative to a base URL.
Discussion
If the URLComponents has an authority component (user, password, host or port) and a path component, then the path must either begin with “/” or be an empty string. If the URLComponents does not have an authority component (user, password, host or port) and has a path component, the path component must not start with “//”. If those requirements are not met, nil is returned.