Presented at the Tokyo iOS Meetup in January, 2017 - in this talk I describe three ways in which you can write cleaner code in Swift.

1. WRITING CLEAN CODE
IN SWIFT
TOKYO IOS MEETUP
JANUARY, 2017 DEREK LEE

2. ANY FOOL CAN
WRITE CODE THAT A
COMPUTER CAN
UNDERSTAND. GOOD
PROGRAMMERS
WRITE CODE
THAT HUMANS CAN
UNDERSTAND.
Martin Fowler

3. … a blog post?
… a research paper?
… a presentation?
SO HOW WOULD YOU WRITE …

4. DRAFT→REVISE

6. REFACTORING
REVISE

7. TDD:
RED
GREEN
REFACTOR

8. How much time do you think you spend
reading code versus writing code?

9. THE RATIO OF TIME SPENT
READING VS. WRITING IS
WELL OVER 10:1.
Robert C. Martin, aka “Uncle Bob”
WRITING CLEAN CODE IN SWIFT

10. 7 12HOURS MINUTES

11. Here are three ways in which you can
immediately improve the readability
of your Swift code

12. #1
USE DESCRIPTIVE
NAMES

13. #1 USE DESCRIPTIVE NAMES
NAMES SHOULD BE…
▸ Intention-revealing: Why it exists, what it does, how it is
used
▸ Pronounceable: Easy to read, not cryptic, using standard
acronyms
▸ Consistent: Choose a single word for a domain concept
and stick with it

14. #1 USE DESCRIPTIVE NAMES
RENAMING IS CONSIDERED REFACTORING
▸ Finding the right name the first time is rare.
▸ Names can and should be revised as needed.
▸ Xcode and AppCode have some automated tools to help
with this process.

15. #1 USE DESCRIPTIVE NAMES
REFACTORING NAMES: XCODE
▸ ⌃ + ⌘ + E → Rename Variable

16. #1 USE DESCRIPTIVE NAMES
REFACTORING NAMES: APP CODE
▸ Shift + F6 → Rename (on pretty much anything)

17. #1 USE DESCRIPTIVE NAMES
func calculate(date1: Date, date2: Date) -> String {
var diff: TimeInterval = 0
if (date2 > date1) {
diff = date2.timeIntervalSince(date1)
} else {
return "No time remaining"
}
let s = Int(diff) % 60
let m = Int(diff / 60) % 60
let h = Int(diff / 3600) % 24
let d = Int(diff / 86400)
return "(d) days, (h) hours, (m) minutes, and (s) seconds remaining"
}

18. #1 USE DESCRIPTIVE NAMES
func calculate(date1: Date, date2: Date) -> String {
var diff: TimeInterval = 0
if (date2 > date1) {
diff = date2.timeIntervalSince(date1)
} else {
return "No time remaining"
}
let s = Int(diff) % 60
let m = Int(diff / 60) % 60
let h = Int(diff / 3600) % 24
let d = Int(diff / 86400)
return "(d) days, (h) hours, (m) minutes, and (s) seconds remaining"
}
let date1 = Date(timeIntervalSince1970: 1484360070) // Jan 14 2017 11:14:30 AM
let date2 = Date(timeIntervalSince1970: 1484557200) // Jan 16 2017 18:00:00 PM
calculate(date1: date1, date2: date2) // 2 days, 6 hours, 45 minutes, 30 seconds
calculate(date1: date2, date2: date1) // No time remaining

19. #1 USE DESCRIPTIVE NAMES
func formatRemainingTime(pastDate: Date, futureDate: Date) -> String {
var secondsDifference: TimeInterval = 0
if (pastDate < futureDate) {
secondsDifference = date2.timeIntervalSince(date1)
} else {
return "No time remaining"
}
let secondsRemaining = Int(secondsDifference) % 60
let minutesRemaining = Int(secondsDifference / 60) % 60
let hoursRemaining = Int(secondsDifference / 3600) % 24
let daysRemaining = Int(secondsDifference / 86400)
let formattedRemainingTime =
String(daysRemaining) + " days, " +
String(hoursRemaining) + " hours, " +
String(minutesRemaining) + " minutes, and " +
String(secondsRemaining) + " seconds remaining"
return formattedRemainingTime
}

20. #1 USE DESCRIPTIVE NAMES
func formatRemainingTime(pastDate: Date, futureDate: Date) -> String {
guard (futureDate > pastDate) else {
return "No time remaining"
}
let secondsDifference = futureDate.timeIntervalSince(pastDate)
let secondsRemaining = Int(secondsDifference) % 60
let minutesRemaining = Int(secondsDifference / 60) % 60
let hoursRemaining = Int(secondsDifference / 3600) % 24
let daysRemaining = Int(secondsDifference / 86400)
let formattedRemainingTime =
String(daysRemaining) + " days, " +
String(hoursRemaining) + " hours, " +
String(minutesRemaining) + " minutes, and " +
String(secondsRemaining) + " seconds remaining"
return formattedRemainingTime
}

21. #2
ORGANIZE YOUR
OBJECTS

22. #2 ORGANIZE YOUR OBJECTS
USE ‘MARK’ ANNOTATIONS FOR CODE ORGANIZATION
▸ // MARK: -
▸ Can be used for:
▸ Defining common parts of objects
▸ Protocol Conformance
▸ Private Methods

23. DEFINE PROPERTIES SEPARATE FROM PROTOCOL CONFORMANCE
#2 ORGANIZE YOUR OBJECTS

24. DEFINE PROPERTIES SEPARATE FROM PROTOCOL CONFORMANCE
{
Properties
+
Initialization
#2 ORGANIZE YOUR OBJECTS

25. DEFINE PROPERTIES SEPARATE FROM PROTOCOL CONFORMANCE
{
Properties
+
Initialization
{Protocol
Conformance
#2 ORGANIZE YOUR OBJECTS

26. DEFINE PROPERTIES SEPARATE FROM PROTOCOL CONFORMANCE
{
Properties
+
Initialization
{Protocol
Conformance
{Private
Methods
#2 ORGANIZE YOUR OBJECTS

27. VIEW CONTROLLER: SHOW DOCUMENT ITEMS: ^ + 6
#2 ORGANIZE YOUR OBJECTS

28. VIEW CONTROLLER: SHOW DOCUMENT ITEMS: ^ + 6
#2 ORGANIZE YOUR OBJECTS

29. VIEW CONTROLLER: SHOW DOCUMENT ITEMS: ^ + 6
#2 ORGANIZE YOUR OBJECTS

30. XCODE SNIPPETS
#2 ORGANIZE YOUR OBJECTS

31. #3
AVOID
COMMENTS

32. EVERY TIME YOU
WRITE A COMMENT,
YOU SHOULD
GRIMACE AND FEEL
THE FAILURE OF
YOUR ABILITY OF
EXPRESSION.
Uncle Bob

33. CREATE A NEW
METHOD INSTEAD
When you feel the need to write a comment…
#3 AVOID COMMENTS

34. A SIMPLE COMPARISON
OR
// Check to see if the employee is eligible for full benefits
if (employee.isHourly && employee.age > 65) {
}
if (employee.isEligibleForFullBenefits()) {
}
#3 AVOID COMMENTS

35. HOW ABOUT DATES?
// Jan 14 2017 11:14:30 AM
let date1 = Date(timeIntervalSince1970: 1484360070)
let Jan_14_2017_11_14_30_AM = Date(timeIntervalSince1970: 1484360070)
OR
#3 AVOID COMMENTS

36. IS THERE SUCH THING AS A GOOD REASON FOR COMMENTS?
▸ Documentation for frameworks or libraries.
▸ Clarification outside of your control (e.g. library usage).
▸ Warning of consequences.
▸ See ‘Clean Code’ for a few more examples.
#3 AVOID COMMENTS

37. WRITING CLEAN CODE IN SWIFT
SUMMARY
1. Use Descriptive Names
2. Organize Your Objects
3. Avoid Comments

39. @DEREKLEEROCK
Thank you!
Tokyo iOS Meetup January 2017