The document discusses best practices for error handling in Swift. It covers defining custom errors, classifying errors as recoverable or non-recoverable, using Result to handle recoverable errors, and throwing errors. The key steps are: 1) defining custom errors, 2) classifying errors, 3) using Result for recoverable errors, 4) throwing errors, and 5) protecting against non-recoverable errors. Recoverable errors can be handled with Result and throwing, while non-recoverable errors require crashing the program or using assertions.

1. THE ART OF FAILING IN
SWIFT
Carlos Vinicius Real
@cviniciusreal

2. Agenda
• Custom Error
• Recoverable x NON-Recoverable
• Throw
• Result

3. Definition
Error handling is the process of responding to and
recovering from error conditions in your program.
Swift Guide, Apple

4. should I use…
PRINT(ERROR)

5. Use case | Sample

6. Use case | Sample

7. WE CAN DO IT BETTER!

8. The Art of Failing
1º step
Getting know your errors

9. Custom Errors | Error protocol

10. The Art of Failing
2º step
Classifying errors

11. The Art of Failing
RECOVERABLE X NON-RECOVERABLE

12. The Art of Failing
RECOVERABLE

13. The Art of Failing
3º step
Result is your friend

14. Recoverable
Result

15. Recoverable | Result

16. Recoverable | Result

17. Recoverable | Result + switch

18. Recoverable | Result + if case

19. The Art of Failing
4º step
Throwing errors, saving lives

20. Recoverable
Throw

21. Pattern | Throw

22. Pattern | Throw
do try try? try! catch

23. Pattern | try?

24. Pattern | try!

25. Pattern | Throw
sample

26. Problems | Throw
rethrow

27. Recoverable | Throw+
How about RxSwift..
Can I throw things there?
!

28. Problems | Throw+
Asynchronous throws

29. The Art of Failing
5º step
Protecting from yourself!
🥃
Are you kidding? My code is perfect!

30. The Art of Failing
NON-RECOVERABLE

31. NON-Recoverable | Result
• assertion/assertionFailure() *
Debug only
• precondition/preconditionFailure() *
Ounchecked optimization mode = on
• fatalError()
• exit()

32. NON-Recoverable | Result
sample

33. QUESTIONS?

34. THANK YOU.
@CVINICIUSREAL