Returns a URL object derived from the components object.
- iOS 7.0+
- macOS 10.9+
- tvOS 9.0+
- watchOS 2.0+
nil, this URL is used as the base URL portion of the resulting URL object.
If the components object 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. Otherwise, this property contains
NSURLComponentsdoes not have an authority component (user, password, host, or port) and has a path component, the path component must not start with
"//". If it does, this property contains