class in playground vs in program file - swift

Question

I have a question about something simple that works in Playground but not in a Project: (Playground code below)
In the project where the class is in a separate swift file the code correction won't show me the the person.lastName and if I fully type it give me an error.... hmm, very strange - might be a beginner error or?
How would I have to state in in the program file and the separate swift file to work?
Thanks,
Roman
import UIKit
class human {
var firstName = ""
var lastName = ""
}
let person = human()
person.lastName = "Smith"
person.firstName = "Peter"
print (person.firstName)
print (person.lastName)

Answer 1

This is why I hate playgrounds. They are not really Swift. In real Swift, all executable code must be inside a function (e.g. a method of some class or struct or enum); you can't have lines like person.lastName = "Smith" just hanging in space like that.
So in a real iOS project you'd need to write something more like this:
class Human {
var firstName = ""
var lastName = ""
}
func test() {
let person = Human()
person.lastName = "Smith"
person.firstName = "Peter"
print (person.firstName)
print (person.lastName)
}
And even then nothing would happen until you actually call test(), and you can't do that except in a function. This is why people usually test code in the viewDidLoad of a view controller.
class Human {
var firstName = ""
var lastName = ""
}
class ViewController : UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let person = Human()
person.lastName = "Smith"
person.firstName = "Peter"
print (person.firstName)
print (person.lastName)
}
}