Using Operators to build error-proof streams

For this section, go ahead and open the project in the code bundle named PublishersAndSubscribers_start. Take a look at the file ViewController.swift.

This file contains a User struct:

struct User: Codable {
  let id: String
  static var unknown: User {
    return User(id: "-1")
  }
}

The User struct is quite simple. It contains a String property id, and a static var named unknown that returns a User instance with id equal to -1. Apart from the User struct, the file contains the ViewController itself.

The view controller contains two methods:

• First, postNotification(): This just fires a notification in the Notification Center that contains a User instance with id equal to 123. The name of the notification is networkResult.
• Second, postNotificationThatFails(): This just fires a notification in the Notification Center that contains random data that is Base...