UIViewController producing values. Example of editing a profile section with a modal interaction, which can produce a new Patient

modalValueProducer.swift

// Create a ViewController automatically wrapped in a UINavigationController
// returns the viewController and a Signal<Patient, NoError>
let (profileVC, signal) = EditPersonalInfoViewController.wrappedInNavigationController(patient: patient)

// observe the signal. When a new Patient is produced, update the view
// dismiss the view controller whenever the signal is completed (i.e. modifications have been saved or interaction has been canceled)
signal.observe(next: reloadViewForPatient, completed: dismissViewController)

// let the game being
self.presentViewController(profileVC, animated: true, completion: nil)