This document discusses Swift programming concepts including value types, optionals, testing, and more. It provides code examples of structs as value types and using optionals to represent missing or incorrect values. It also shows how to create a Person model and PersonViewModel, add input validation to the view model using enums and errors, and handle errors when creating a person from the view model.

1. Swift Thinking
@NatashaTheRobot

2. @NatashaTheRobot
• Swift Newsletter -
swiftnews.curated.co
• NatashaTheRobot.com

3. Learning…

4. Work with Others

5. Teach

6. Put Your Stuff Out
There

7. Expose Yourself to
Advanced Topics

8. Celebrate
Breakthroughs

9. @ashsmash

10. Learning…
• Value Types
• Optionals?!
• Testing

11. Value Types

12. • structs
• enums
• (tuples)

13. class Person {
let name: String
var age: Int
init(name: String, age: Int) {
self.name = name
self.age = age
}
}

14. let taylorSwift = Person(name: "Taylor Swift", age: 25)
func timeTravelToBirthdayForPerson(var person: Person) {
person.age += 1
()
}
timeTravelToBirthdayForPerson(taylorSwift)
taylorSwift.age // 26

15. let taylorSwift = Person(name: "Taylor Swift", age: 25)
func timeTravelToBirthdayForPerson(person: Person) {
person.age += 1
🎉🎂🎁🎈💥()
}
timeTravelToBirthdayForPerson(taylorSwift)
taylorSwift.age // 26

16. let taylorSwift = Person(name: "Taylor Swift", age: 25)
func timeTravelToBirthdayForPerson(var person: Person) {
person.age += 1
🎉🎂🎁🎈💥()
}
timeTravelToBirthdayForPerson(taylorSwift)
taylorSwift.age // 26

17. struct Person {
let name: String
var age: Int
// NO INIT NEEDED
}

18. let taylorSwift = Person(name: "Taylor Swift", age: 25)
func timeTravelToBirthdayForPerson(var person: Person) {
person.age += 1
()
}
timeTravelToBirthdayForPerson(taylorSwift)
taylorSwift.age // 25

19. let taylorSwift = Person(name: "Taylor Swift", age: 25)
func timeTravelToBirthdayForPerson(var person: Person) {
person.age += 1
🎉🎂🎁🎈💥()
}
timeTravelToBirthdayForPerson(taylorSwift)
taylorSwift.age // 25

20. let taylorSwift = Person(name: "Taylor Swift", age: 25)
func timeTravelToBirthdayForPerson(var person: Person) {
person.age += 1
🎉🎂🎁🎈💥()
}
timeTravelToBirthdayForPerson(taylorSwift)
taylorSwift.age // 25

21. let taylorSwift = Person(name: "Taylor Swift", age: 25)
func timeTravelToBirthdayForPerson(var person: Person) {
person.age += 1
🎉🎂🎁🎈💥()
}
timeTravelToBirthdayForPerson(taylorSwift)
taylorSwift.age // 25

23. @andy_matuschak
• Functional Swift Conference: Functioning as a
Functionalist
• Realm: Controlling Complexity in Swift

24. –Functional Swift Book
“Almost all types in Swift are value types,
including arrays, dictionaries, numbers,
booleans, tuples, and enums. Classes are the
exception rather than the rule.”

25. $ grep -e "^struct " swift.md | wc -l
87
$ grep -e "^enum " swift.md | wc -l
8
$ grep -e "^class " swift.md | wc -l
4

26. Optionals?!

28. –Sunset Lake Software
“~40% of bugs shipped to customers in the last
three years would have been caught
immediately by using Swift”

29. Objc.io Issue 13

31. struct Person {
let name: String
var age: Int
}

32. struct PersonViewModel {
var name: String?
var age: String?
}

33. class ViewController: UIViewController, UITextFieldDelegate {
@IBOutlet weak var nameTextField: UITextField!
@IBOutlet weak var ageTextField: UITextField!
var personViewModel = PersonViewModel()
override func viewDidLoad() {
super.viewDidLoad()
}
func textFieldDidEndEditing(textField: UITextField) {
personViewModel.name = nameTextField.text
personViewModel.age = ageTextField.text
}
}

34. struct PersonViewModel {
var name: String?
var age: String?
enum InputError: ErrorType {
case InputMissing
case AgeIncorrect
}
func createPerson() throws -> Person {
guard let age = age, let name = name else {
throw InputError.InputMissing
}
guard let ageFormatted = Int(age) else {
throw InputError.AgeIncorrect
}
return Person(name: name, age: ageFormatted)
}
}

35. class ViewController: UIViewController, UITextFieldDelegate {
var personViewModel = PersonViewModel()
// ... truncated ... //
@IBAction func onSubmitButtonTap(sender: AnyObject) {
view.endEditing(true)
do {
let person = try personViewModel.createPerson()
print("Success! Person created. (person)")
} catch PersonViewModel.InputError.InputMissing {
print("Input missing!")
} catch PersonViewModel.InputError.AgeIncorrect {
print("Age Incorrect!")
} catch {
print("Something went wrong, please try again!")
}
}
}

36. Failable initializers, revisited
@jesse_squires

37. Testing

38. • Performance Tests
• Asynchronous Tests
• Xcode CI Improvements
• UI Tests
• Code Coverage

43. Still Learning…
• Value Types
• Optionals?!
• Testing

44. To Learn…
• do
• guard
• defer
• error handling
• protocol extensions
• print
• pattern matching
• early exits
• UI Testing
• WatchOS
• UIStackView
• Security
• Complications
• Continuous Integration
• App Thinning
• Crash Logs
• Objective-C Generics