Migration Swift 3 by David Bonnet

1. LET’S MIGRATE TO 3.0
COCOAHEADS NANTES
David Bonnet - @iGranDav
19 January 2017

2. A LITTLE BIT OF HISTORY…
▸ From Swift 1.x to Swift 2.x
▸ Just remember ErrorType and throwable types
▸ Swift 3.0 is the first community version !
🎉 "
‣ it also breaks code ! 😅

3. ⚠
STILL NOT ABI STABLE !
Everything needs to be migrated

4. LET’S DO IT SOFTLYSWIFT 2.3

5. LET’S DO IT SOFTLY - SWIFT 2.3
A LIGHTWEIGHT UPDATE
▸ Only takes advantage of Nullability Checking on Objective-C Interoperability
// Swift 2.2
let image = CIImage(MTLTexture: texture, options: options)
let extent = image.extent // this code can lead to a crash
// Swift 3.0
if let image = CIImage(MTLTexture: texture, options: options) {
…
}
▸ This can help you migrate quickly to the SDK 10 on a big base code %
5

6. LET’S DO IT SOFTLY - SWIFT 2.3
A TEMPORARY SOLUTION
▸ Xcode loses code sense (even more than usual)
▸ Sometimes completion code is absent / No code coloration when lost
▸ When showing real-time errors in source code, Xcode can get lost
▸ this is valid swift 2.3 code ! and it builds 🤕
▸ fixed in latest Xcode 8.2.1
▸ Xcode 8.2.x is the last version to support it! 😈
6

7. OK NOW FOR REALSWIFT 3.0

8. APPLE SOLUTION
LET’S MIGRATE - SWIFT 3.0

9. LET’S MIGRATE - SWIFT 3.0
APPLE SOLUTION - MIGRATION ASSISTANT
9

10. LET’S MIGRATE - SWIFT 3.0
APPLE SOLUTION - MIGRATION ASSISTANT IN REAL LIFE
10
😱 Using Xcode 8.0

11. AN APPROACH
LET’S MIGRATE - SWIFT 3.0

12. LET’S MIGRATE - SWIFT 3.0
1. MIGRATE YOUR DEPENDENCIES - COCOAPODS / CARTHAGE
▸ Long live Objective-C! 👻
▸ Almost nothing to do here…
▸ Some authors have annotated their libraries: better swift interoperability!
▸ Others have created a brand new swift version:
▸ MMDrawerController has been converted to DrawerController
drawerController?.openDrawerGestureModeMask = MMOpenDrawerGestureMode.None
[X] ’None' has been renamed to 'none'
12
https://github.com/mutualmobile/MMDrawerController/issues/476
drawerController?.openDrawerGestureModeMask = MMOpenDrawerGestureMode.none
[X] 'none' is unavailable: use [] to construct an empty option set

13. LET’S MIGRATE - SWIFT 3.0
1. MIGRATE YOUR DEPENDENCIES - COCOAPODS / CARTHAGE
▸ ⚠ update your libraries means update also their APIs or introduce new features!
extension Results {
func toArray() -> [T] {
return self.map {$0}
}
}
extension RealmSwift.List {
func toArray() -> [T] {
return self.map {$0}
}
}
13
=>
//New definition in RxRealm
extension List: NotificationEmitter {
public typealias ElementType = Element
public func toArray() -> [Element] {
return Array(self)
}
}

14. 14
▸ Migrate your code template before the migration!
▸ SwiftGen - https://github.com/AliSoftware/SwiftGen
-t swift3
LET’S MIGRATE - SWIFT 3.0
2. USING A CODE GENERATOR?
#!/bin/sh
swiftgen strings

15. 15
▸ Use a linter? Disable it during the migration.
▸ SwiftLint - https://github.com/realm/SwiftLint
1. Launch the migration assistant on your targets only
2. Analyse each source file:
1. Fix it if needed 😅
2. Uncheck from migration when it’s a third party file 😓
3. Do not hesitate to pass the migrator several times
LET’S MIGRATE - SWIFT 3.0
3. SOME OTHER THINGS

16. REAL WORLD PROBLEMSSHARING ISSUES AND FIXING THEM +

17. 17
▸ To avoid renaming all your APIs calls:
▸ _ is automatically added, you probably want to name them properly
func updateIdentityWithName(_ name: String, firstname: String) throws
▸ Some Foundation objects with deleted NS prefix are casted to conform to
new APIs
let url = NSURL(string: "http://someurl.com" )
URLComponents(url: url as URL, resolvingAgainstBaseURL: false)
REAL WORLD PROBLEMS
BEWARE SOME CHANGES ARE MADE AUTOMATICALLY
SE-0046
if let url = URL(string: "http://someurl.com" ) {
URLComponents(url: url, resolvingAgainstBaseURL: false)
}
func updateIdentity(name: String, firstname: String) throws

18. 18
▸ A cast to AnyObject is frequently added although new APIs accept Any
▸ Convert your JSON objects to [String: Any]
▸ ⚠ Some types becomes values types!
▸ public struct Date versus open class NSDate
▸ But it can simplify the reading:
▸ (x as NSDate).earlierDate(y) can be changed to x < y ? x : y
REAL WORLD PROBLEMS
BEWARE SOME CHANGES ARE MADE AUTOMATICALLY
https://developer.apple.com/swift/blog/?id=39

19. 19
▸ Your potential if let or guard let on absoluteString will not be
removed, it’s your job 🙂
▸ Tip: If you absolutely need to keep your code block you can use a do
statement
REAL WORLD PROBLEMS
SOME APIS DO NOT RETURN OPTIONALS ANYMORE
open class NSURL {
open var absoluteString: String? { get }
}
public struct URL {
public var absoluteString: String { get }
}
versus
do {
//your code here
}

20. REAL WORLD PROBLEMS
OPTIONAL COMPARATORS DISAPPEARED
20
// FIXME: comparison operators with optionals were removed from the Swift Standard Libary.
// Consider refactoring the code to use the non-optional operators.
fileprivate func > <T: Comparable>(lhs: T?, rhs: T?) -> Bool {
switch (lhs, rhs) {
case let (l?, r?):
return l > r
default:
return rhs < lhs
}
}

21. 21
▸ Dispatch APIs are not correctly migrated (at least at that time using Xcode 8.0)
DispatchQueue.global(qos: .background).async {
//do some work
}
DispatchQueue.global(qos: .default).asyncAfter(deadline: .now() + 1) {
//do some work in 1s from now
}
▸ dispatch_once doesn’t exist anymore 😢
▸ Use lazily initialised globals or static properties 😎
REAL WORLD PROBLEMS
GRAND CENTRAL DISPATCH
SE-0044 & SE-0088

22. 22
▸ Remember Nullability Checking integrated into Swift 2.3
▸ ImplicitlyUnwrappedOptionals are considered like optionals now, but not
all the time 😅
REAL WORLD PROBLEMS
OBJECTIVE-C INTEROPERABILITY
https://www.natashatherobot.com/swift-3-implicitly-unwrapped-optionals/
because File > New Project is a rare thing
func valueUp(value: Int!) {
// oldValue is an Int?
// since value doesn't need to be type checked
let oldValue = value // Int?
// newValue is an Int,
// since value was forced to unwrap
// b/c it had to be type checked to do the addition
let newValue = value + 1 // Int
[…]
}
valueUp(value: 10)

23. 23
▸ Swift 3 renamed a lot of objective-c based APIs automatically "
▸ Legacy swift annotations are still available
▸ nullability / generics
▸ NS_SWIFT_NAME / NS_REFINED_FOR_SWIFT / NS_SWIFT_UNAVAILABLE
▸ New annotations available
▸ NS_NOESCAPE to annotate your objective-c blocks (eg. @noespace)
▸ NSEXTENSIBLESTRING_ENUM to convert a string based obj-c enum to a struct
REAL WORLD PROBLEMS
OBJECTIVE-C INTEROPERABILITY
https://realm.io/news/altconf-nikita-lutsenko-objc-swift-interoperability/
because File > New Project is a rare thing

24. 24
▸ I had to convert manually CGFloat.max to CGFloat.greatestFiniteMagnetude
▸ OptionSet are not converted as expected for default values :
▸ UIControlState() instead of .normal : it works but less readable
▸ Visibility changes : private becomes fileprivate etc…
▸ ⚠ Be aware of open versus public on your libraries
REAL WORLD PROBLEMS
SOME RANDOM NOTES
SE-0067

25. 25
▸ map or flatmap returns LazyCollection types now :
▸ let list = Array(myLazyCollection) if you really need a Collection
▸ New compiler : new warnings like unused results 👾
▸ You can add _ to discard it: _ = foo()
▸ returned result is secondary: @discardableResult on the function can
also avoid this warning
REAL WORLD PROBLEMS
SOME RANDOM NOTES
SE-0067

26. QUESTION TIMETHANKS FOR YOUR ATTENTION 😀

27. 27
▸ A (mostly) comprehensive list of Swift 3.0 and 2.3 changes
▸ https://buildingvts.com/a-mostly-comprehensive-list-of-swift-3-0-and-2-3-changes-193b904bb5b1
▸ Swift migration guide
▸ https://swift.org/migration-guide/
▸ WWDC 2016 - Session 402 : What’s new in swift
▸ https://developer.apple.com/videos/play/wwdc2016/402/
▸ AltConf - Advanced ObjC <-> Swift Interoperability
▸ https://realm.io/news/altconf-nikita-lutsenko-objc-swift-interoperability/
LET’S MIGRATE TO 3.0
REFERENCES
David Bonnet - @iGranDav
david.bonnet@cocoaheads.fr