HAKATA.swift at Fukuoka Engineers Day 2019 Summer

1. What Swifty is, from Swift Enumeration
freddi from HAKATA.swift
at Fukuoka Engineers Day 2019 (20. July)

2. About Me
freddi (Yuki Aki)
iOS Engineer at LINE Fukuoka
Organizer of HAKATA.swift

3. About HAKATA.swift
Community of Swift Language
Holding Event per 2 month

4. About HAKATA.swift

5. About HAKATA.swift
8/24 at SALT

6. What is Swifty?

7. What is Swifty?
from Satoshi Hachiya - What is `Swifty`?
https://medium.com/swift-column/what-is-swifty-34e3b2625e31

8. What is Swifty?
from Swift.org - About Swift
https://swift.org/about/
• Safe
• Fast
• Expressive

9. Using Expressive Code is one of Swifty?
What is Swifty?

10. Only Expressive Code is Swifty?
What is Swifty?

11. Expressive Code
with using Swift feature is Swifty!
What is Swifty?

12. Enumeration in Swift

13. Swift Enumeration is one of way to
make expressive code
Enumeration in Swift

14. Enumeration in Swift
enum Selection {
case yes
case no
}

15. Enumeration in Swift
let selection: Selection = Selection.yes
enum Selection {
case yes
case no
}

16. • Swift Enumeration is expressive!
• Type Inference in Enumeration
• Associated Values in Enumeration
Enumeration in Swift

17. Type Inference in Enumeration

18. Type Inference in Enumeration
let selection: Selection = Selection.yes
enum Selection {
case yes
case no
}

19. Type Inference in Enumeration
let selection: Selection = .yes
enum Selection {
case yes
case no
}

20. Type Inference in Enumeration

21. Associated Values in Enumeration

22. Let’s make Type
• Representing the result of REST API
Associated Values in Enumeration

23. Associated Values in Enumeration
enum APIResult {
case success
case error
}

24. But, we have some situation at using REST API
• What Error Returned?
• Validation Error?
• Authorization Error?
Associated Values in Enumeration

25. Associated Values in Enumeration
enum APIResult {
case success
case validationError
case authError
}

26. Let’s use Associated Values to represent situations
Associated Values in Enumeration

27. Associated Values in Enumeration
enum APIResult {
case success
case error
}

28. Associated Values in Enumeration
enum APIResult {
case success
case error(Error)
}

29. Associated Values in Enumeration
let result: APIResult = .success
enum APIResult {
case success
case error(Error)
}

30. Associated Values in Enumeration
let result: APIResult = .error(ValidationError())
enum APIResult {
case success
case error(Error)
}
let result: APIResult = .success

31. Associated Values in Enumeration
• Each case can have values
Associated Values in Enumeration

32. Let’s make APIResult More Generic
Associated Values in Enumeration

33. Associated Values in Enumeration
enum APIResult {
case success
case error(Error)
}

34. Associated Values in Enumeration
enum APIResult<SuccessType> {
case success(SuccessType)
case error(Error)
}

35. Associated Values in Enumeration
func getXXX(result: APIResult<SomeData>) {
switch result {
case .success(let data):
...
case .error(let error):
...
}
}

36. Optional in Swift

37. Enumeration in Swift

38. Swift Enumeration is Expressive!

39. let selection: Selection = .yes
enum Selection {
case yes
case no
}
Swift Enumeration is Expressive!

40. let result: APIResult = .error(ValidationError())
enum APIResult {
case success
case error(Error)
}
let result: APIResult = .success
Swift Enumeration is Expressive!

41. Swift Enumeration is Expressive!
enum APIResult<SuccessType> {
case success(SuccessType)
case error(Error)
}

42. Why expressive is great?

43. To be Expressive Helps our coding life
Why expressive is great?

44. Why expressive is great?

45. Why expressive is great?
enum APIResult {
case success
case error(Error)
}

46. Why expressive is great?
let result: APIResult = .error(ValidationError())
enum APIResult {
case success
case error(Error)
}

47. Why expressive is great?
enum ValidationError: Error {
case nameIsInvalid
case idIsInvalid
}
let result: APIResult = .error(ValidationError())

48. Expressive is one of Swifty
Expressive is great!

49. Swifty and Enumeration

50. Thank you for listening!

51. 8/24 at SALT