Ash Furrow shares his recent real-world experience with Swift as a case study in an evaluation of Swift's production readiness. He provides a chance of taking advantage of the lessons they learned to make the best decisions about Swift.

1. Ash Furrow, Artsy
Lessons
from
Production Swift

2. February, 2014

3. Swift
Let’s talk about

4. 1. The Need for Swift
2. The Fast and the Faulty
3. Seek Out Bold New Worlds

5. Need
Swift
The
for

6. Objective-C

7. TXS ;push return address back onto stack
LDY #$00 ;load Y with zero - will hold result
LOOP1 LDAA TEMP ;load A into TEMP
ANDA MASK ;AND A with Mask
BNE ADD1
BRA NONE1
ADD1 INY ;increment our counter of 1's
NONE1 LDAA TEMP ;reload accumulator A
LSL MASK ;Shift the mask's 1 bit left
BNE LOOP1 ;If we haven't finished our loop, branch
LDAA #$01 ;load new mask into A
STAA MASK ;store the reset mask into MASK
TSX ;pull of return address and store in X
PULA ;pull off A
STAA TEMP ;store the value into temp
TXS ;push return address back onto the stack
LOOP2 LDAA TEMP ;Load A into TEMP
ANDA MASK ;logical AND MASK with A
BNE ADD2 ;add one if we need to
BRA NONE2
ADD2 INY ;increment our counter of 1's
NONE2 LDAA TEMP
LSL MASK ;shift our mask left by one
BNE LOOP2 ;loop back until we've exhausted positions
STY TEMP ;store Y into TEMP - this is the number of 1's
LDAB TEMP ;load the number of 1's into B
LDAA #$10 ;load dec 16 into A
SBA ;A - B -> A same as 16 - B -> A

8. —John Siracusa
“While hardware performance increases over time,
the human capacity to deal with complexity does not.”

9. Stuck
Objective-C
Past
is
in the

10. Beyond Hope
Objective-C
is

11. Criteria
1. No C baggage
2. Memory Managed
3. Native unicode strings
4. Native collections
5. Be concise
6. Named Parameters

12. Criteria
1. No C baggage
2. Memory Managed
3. Native unicode strings
4. Native collections
5. Be concise
6. Named Parameters
😋
😅
😃
😄
😍
😎

13. The Need for Swift
• Programming abstraction increases over time
• Objective-C has improved all it can
• Swift is the next step
• Revolution, not evolution

14. Fast
Faulty
The
and the

15. Problems In Beta
• Xcode crashes
• Compiler segfaults
• Constant changes to Swift
• Many language limitations

16. Problems Now
• Still some stability issues
• Still frequent changes to Swift
• Still some remaining language limitations

17. Problems Now
• Language changes tied to Xcode versions
• Runtime changes tied to Xcode versions
• Changes in resource-loading in frameworks

18. Community Tools
• Most still in their infancy
• CocoaPods, Jazzy, SBConstants…
• The rest do not exist
• Test coverage analyzer

19. Community Libraries
• Struggling to accomodate frequent Swift changes
• Xcode updates make this difficult

20. The Fast and the Faulty
• Swift had a rough start
• Was to be expected
• Things are better now
• Mostly
• Growing pains

21. Seek Out
New Worlds
Bold

22. Problem Solving in Objective-C
Problem Solving in Swift
is not

23. Examples

24. Index Paths
• Used to identify cells in a table view
• Section, row
• Lots of horrendous code
• It’s so bad
• Seriously bad

25. Index Paths
if (indexPath.section == 0) {
if (indexPath.row == 0) {
} else if (indexPath.row == 1) {
} else if ...
} else if (indexPath.section == 1) {
if (indexPath.row == 0) {
} else if (indexPath.row == 1) {
} else if ...
} else if ...

26. Index Paths
if (indexPath.section == 0) {
if (indexPath.row == 0) {
} else if (indexPath.row == 1) {
} else if ...
} else if (indexPath.section == 1) {
if (indexPath.row == 0) {
} else if (indexPath.row == 1) {
} else if ...
} else if ...

27. Index Paths
switch (indexPath.section, indexPath.row) {
case (0, 0):
case (0, 1):
case (1, 0):
case (1, 1):
default:
// nop
}

28. Still Terrible
This is

29. Index Paths
switch (indexPath.section, indexPath.row) {
case (0, let row):
// Executed for any section 0, row is row
case (let section, 0) where section % 2 == 1:
// Executed for first rows of odd all sections
case (let section, let row) where validate(section):
// Executed when validate() returns true
default:
// Executed on all other cases
}

30. Generics
• Define functions, structs, others in the abstract
• Create one instead of many
• Arrays, dictionaries, and sets are all generics

31. Generics
struct Stack<T> {
private var contents = Array<T>()
mutating func push(value: T) {
contents.insert(value, atIndex: 0)
}
mutating func pop() -> T {
return contents.removeAtIndex(0)
}
var isEmpty: Bool {
return countElements(contents) == 0
}
}

32. Generics
var intStack = Stack<Int>()
var stringStack = Stack<String>()
var stackStack = Stack<Stack<AnyObject>>()
intStack.push(1)
intStack.pop() // Returns 1

33. Lazy Loading
• Create resource when it is first accessed
• Avoids unnecessary work for CPU
• Avoids unnecessary memory use

34. Lazy Objective-C
• No language-level support
• Lots of repetition
• Tedious work
• Lots of repetition

35. Lazy Objective-C
@interface MyClass: NSObject
@property (nonatomic, strong) Name *name;
@end
@implementation
- (Resource *)resource {
if (_resource == nil) {
_resource = "Ash Furrow";
}
return _resource
}
@end

36. Lazy Swift
class MyClass {
lazy var name = "Ash Furrow"
}

37. Lazy Swift
class MyClass {
lazy var name = "Ash Furrow"
}
MyClass().name // Returns "Ash Furrow"
let instance = MyClass()
instance.name = "Orta Therox"
instance.name // Returns “Orta Therox"

38. Lazy Swift
class MyClass {
lazy var name = "Ash Furrow”
lazy var greeting: String = {
return "Hello, (self.name)"
}()
}
MyClass().greeting // Returns "Hello, Ash Furrow"
let instance = MyClass()
instance.name = "Orta Therox"
instance.greeting // Returns "Hello, Orta Therox"
instance.name = "Eloy Durán"
instance.greeting // Returns "Hello, Orta Therox"

39. Extending Types
• Objective-C has “categories” for extending
existing classes
• Swift has “extensions” instead
• They work on all types

40. Extending Types
extension Int {
func times(closure: () -> ()) {
for i in 0..<self {
closure()
}
}
}
4.times {
// Do something 4 times
}

41. Extending Types
extension Int {
var hours: NSTimeInterval {
return NSTimeInterval(3600 * self)
}
}
extension NSTimeInterval {
var fromNow: NSDate {
return NSDate(timeIntervalSinceNow: self)
}
var ago: NSDate {
NSDate(timeIntervalSinceNow: -self)
}
}
4.hours.fromNow
4.hours.ago

42. Functional Awesomeness
let people = ["Carter", "Sebastian", "Daniel"]
people.map { "Hello, ($0)!" }
func hello(name: String) -> String {
return "Hello, (name)!"
}
people.map(hello)
or…

43. Functional Awesomeness
func say(greeting: String) -> (name: String) -> String {
return { (name: String) -> String in
"(greeting), (name)!"
}
}
people.map(say("Hello"))
people.map(say("Merhaba"))

44. Functional Awesomeness
func say(greeting: String)(name: String) -> String {
return "(greeting), (name)!"
}
people.map(say("Hello"))
people.map(say("Merhaba"))

45. SBConstants
• Generate constants for Storyboard identifiers
• Compile-time checked enum
• Can be extended…

46. SBConstants
func performSegue(identifier: SegueIdentifier) {
performSegueWithIdentifier(identifier.rawValue, sender: self)
}
...
func ==(lhs: UIStoryboardSegue, rhs: SegueIdentifier) -> Bool {
return lhs.identifier == rhs.rawValue
}

47. SBConstants
peformSegue(.RegisterCreditCard)
...
func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue == .RegisterCreditCard {
...
}
}

48. SBConstants
• Don’t use rawValue all over the place
• Abstract it away
• Get compile-time safety

49. Familiar Problems
New Ways
to solve
Let’s look for

50. For Advice
Ask
other communities
Let’s

51. Resources
• Natasha the Robot’s newsletter
• iOSDevWeekly
• iOS Goodies
• GitHub Explore
• leanpub.com/yourfirstswiftapp

52. Eidolon

53. 1. The Need for Swift
2. The Fast and the Faulty
3. Seek Out Bold New Worlds

54. Better Mistakes
Make
Tomorrow