Kyle Sherman: Swift at Linkedin

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December 11, 2015

Kyle Sherman: Swift at Linkedin

When Apple first announced Swift, iOS developers across LinkedIn started learning it. This deck by Software Engineers Kyle Sherman and Kamilah Taylor describes LinkedIn's experience with writing 2 drastically different apps in Swift.

The SlideShare app has a much smaller user base, number of developers, and fewer features. The new LinkedIn app, Project Voyager, is a very large codebase with a large group of developers and a huge user base. This should give you the idea of what type of challenges and benefits both a startup and large company would have by switching to Swift from Objective-C.

This presentation was given at the Sillicon Valley iOS Developers' Meetup on 12/07/2015. Thanks to Tim Burks for hosting and organizing the event.

Follow Kamilah on Twitter & LinkedIn:

Follow Kyle on Twitter & LinkedIn:



December 11, 2015


  1. 2.

    2 Perspectives • Kyle represents SlideShare app • 4 devs,

    ~3 months for v1 • Kamilah represents Voyager • Recently released LinkedIn app rewrite • ~50 devs, ~1 year for v1
  2. 4.
  3. 6.

    SlideShare • Timing was right; had just started development •

    Interoperability with ObjC • Most of team coming from Ruby • Safety Features slideshare
  4. 8.

    LinkedIn Flagship App • Immediately started learning Swift • Tested

    Swift for new iOS features on current app • Today widget • Share extension
  5. 10.

    Project Voyager • Engineering discussions for app just started •

    Another complete rewrite wouldn’t happen soon • Concerned with potential pain of switching to Swift later • Engineers were excited about language features of Swift like optionals
  6. 14.

    Early Days (Betas) • Syntax Highlighting and Autocomplete slow •

    Select few classes had to be ObjC (IB support)
  7. 19.

    Xcode • Compile times very very very long for large

    codebase (~25 min on 15” rMBP) • Migration tool crashed on large codebase • App binary size was large and load time had increased
  8. 20.

    Workarounds (Voyager) • Code structure • Dropped iOS 7 support

    • Modularized using Cocoapod's devpods • This broke debug symbols • Converted devpods into dynamic frameworks
  9. 21.

    Workarounds (Voyager) • Lengthy, manual migration to new Swift version

    • Xcode 7.0 decreased build times dramatically (+26% speed boost) • Switched generated models to ObjC (to reduce the number of Swift files) • Mac Pros for everyone! (12 cores gave us a 2x speed boost over the top of the line MBP)
  10. 22.

    Workarounds (Voyager) • Xcode 7 reduced app binary size by

    15% • Increased cold launch time in iOS 9 due to Apple bug that lead to increase in time to load libraries (especially enterprise builds) • Converted some dynamic libraries to static
  11. 23.
  12. 24.

    SlideShare • Syntax way cleaner and easy for newcomers •

    Optionals, initialization rules, static typing, etc. much safer • Less crashes by using optionals and asserting instead of crashing
  13. 25.

    Voyager • Whole classes of bugs disappeared (i.e. NPE) long

    as you never force unwrap optionals! • Caveat - ObjC libraries that have not been annotated for Swift
  14. 26.

    Voyager • Swift lint • Easier to onboard devs from

    web or Java • Especially noticeable with how fast it was for interns to learn Swift • Community is very active and helpful • Functional programming
  15. 27.
  16. 28.

    SlideShare • We have not integrated any Swift libraries •

    Upgrading causes some problems with internal code because of our Today extension
  17. 29.

    Voyager • Most internal libraries are still written in ObjC

    • We have some internal and external libraries, written in Swift, integrated • Cocoapods is how we do all dependency management
  18. 31.

    Key Takeaways for teams • It will be faster for

    you to train new devs on Swift • Less newbie ObjC errors
  19. 32.

    Key Takeaways for teams • ObjC is still a valid

    option and will have less issues • There are still Swift bugs that will cause crashes in your app • You won't spend time on workarounds for the language and the tools with ObjC
  20. 33.

    Key Takeaways for teams • Managing Xcode version still a

    pain • For example, bugs in iOS 8.1, Xcode 6.1, Swift 1.2, etc • It took months to upgrade to Xcode 7.2
  21. 34.

    Great Time to Start! • Xcode 7 and Swift 2

    are much more stable • Build times are significantly improved
  22. 40.

    If You Have an ObjC App • Code new features

    in Swift; get familiar with it • Go back and refactor ObjC where you would see a benefit • Don’t recommend rewriting entire app unless planning a rewrite for other reasons
  23. 42.

    Considerations for Swift • Less time spent on-boarding new developers

    (much less than ObjC) • Fewer mistakes made and bugs created (much fewer) • More workarounds needed for tooling and code (considerable issue for large teams)