Step1.swift

struct Person {
  let name: String
  let address: String
}

struct ViewModel {
  var person: Person
  var nameAndAddress: String {
    return "\(person.name), \(person.address)"
  }
  
  init() {
    person = Person(name: "John Appleseed", 
                    address: "1 Infinite Loop, Cupertino, CA")
  }
}