This content was released on Dec 4 2017. The official support period is 6-months from this date.
In the past working with JSON meant using either NSJSONSerialization class or a third party library. Now it's a matter of implementing a simple protocol.
This is a companion discussion topic for the original entry at https://www.kodeco.com/4035-ios-11-screencasts-what-s-new-in-foundation/lessons/1