Seattle Kotlin: Adopting Kotlin

Talk given at Seattle Kotlin meetup event on Feb 20, 2018

https://www.meetup.com/Seattle-Kotlin/events/247789031/

Focus on Udacity's adoption of Kotlin as the primary development language for the Android engineering team

More Kotlin From Udacity:

Posts:
https://engineering.udacity.com/adopting-kotlin-c12f10fd85d1

https://engineering.udacity.com/learning-kotlin-by-mistake-b99304b7d724

https://engineering.udacity.com/modeling-viewmodel-states-using-kotlins-sealed-classes-a5d415ed87a7

Udacity Course:
https://www.udacity.com/course/kotlin-for-android-developers--ud888

Contact Me:
https://twitter.com/n8ebel
https://n8ebel.com/
https://medium.com/@n8ebel

Transcript

1. Adopting Kotlin
   A case study in team buy-in and adoption
   © @n8ebel, Udacity Engineering 2018 1
   

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2. What Is Kotlin?
   » a programming language
   developed by JetBrains
   » targets the JVM
   » is 100% compatible with
   Java for Android
   development
   © @n8ebel, Udacity Engineering 2018 2
   

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3. Where Is It Used?
   » Android
   » JVM
   » Browser
   » Backend
   » iOS
   © @n8ebel, Udacity Engineering 2018 3
   

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4. Adoption at Udacity
   © @n8ebel, Udacity Engineering 2018 4
   

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5. Production Today
   Have been using in production
   for over a year
   Today, Kotlin is our primary
   development language for
   Android
   © @n8ebel, Udacity Engineering 2018 5
   

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6. Why Invest In Kotlin?
   » Our adoption process
   » How are we using Kotlin today
   » Tips for incorporating Kotlin into your project
   © @n8ebel, Udacity Engineering 2018 6
   

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7. Why Kotlin?
   © @n8ebel, Udacity Engineering 2018 7
   

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8. “Kotlin provides a more
   enjoyable developer
   experience by allowing us
   to express our features &
   ideas using safer, more
   concise code. This, in turn,
   enables us to build a better
   product for our users”
   © @n8ebel, Udacity Engineering 2018 8
   

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9. Key Benefits
   » Improved crash rate
   » Reduction in lines of code written
   » Decreased time spent in code review
   » Renewed excitement around experimentation and
   innovation
   © @n8ebel, Udacity Engineering 2018 9
   

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10. Ultimately, our goal is to
    provide our users with the
    best learning experience
    possible.
    © @n8ebel, Udacity Engineering 2018 10
    

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11. We believe Kotlin helps us do that.
    © @n8ebel, Udacity Engineering 2018 11
    

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12. How Did We Start?
    © @n8ebel, Udacity Engineering 2018 12
    

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13. Recognition of Pain Points
    We started to notice patterns in our code reviews
    » “we need to be consistent in our handling of null”
    » “this code could be shortened using a more
    functional approach”
    © @n8ebel, Udacity Engineering 2018 13
    

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14. Recognition of Pain Points
    Having experimented with Kotlin outside Udacity, we
    knew the language could help with some of these
    issues
    © @n8ebel, Udacity Engineering 2018 14
    

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15. Kotlin, Meet the Team
    » built a small new feature
    » create both a Java & Kotlin
    PR
    » demonstrated that Kotlin
    could be easily integrated
    © @n8ebel, Udacity Engineering 2018 15
    

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16. Jumping Off Point
    » Set out to migrate our Settings screen
    » During testing, we looked closely for 2 things
    © @n8ebel, Udacity Engineering 2018 16
    

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17. Jumping Off Point
    1.Usability issues: what impact did Kotlin have on
    crashes/bugs?
    2.Development process: did Kotlin cause CI issues,
    slow down our build, or slow down feature
    development?
    © @n8ebel, Udacity Engineering 2018 17
    

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18. Ship It
    As expected, no significant
    issues found
    Released to production
    © @n8ebel, Udacity Engineering 2018 18
    

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19. Slow Down
    At this point, we slowed down a bit.
    We loved using Kotlin, but recognized the potential
    risks of going all-in on an unofficially supported
    language.
    We continued to add/convert some tests to Kotlin, but
    no new feature code was using it
    © @n8ebel, Udacity Engineering 2018 19
    

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20. Game Changer
    © @n8ebel, Udacity Engineering 2018 20
    

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21. Google I/O
    The Google I/O announcement
    of official support for
    Kotlin was the push we needed
    We decided immediately that
    we wanted to go all-in on
    Kotlin
    © @n8ebel, Udacity Engineering 2018 21
    

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22. Team Buy In
    Met with our PM and expressed our desire/plan to
    adopt Kotlin.
    We were met with a healthy dose of pragmatism.
    © @n8ebel, Udacity Engineering 2018 22
    

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23. “What’s the value prop?”
    » Is the language stable/safe to be using now?
    » Will it slow down development?
    » Are there tangible benefits?
    © @n8ebel, Udacity Engineering 2018 23
    

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24. Migration Plan
    © @n8ebel, Udacity Engineering 2018 24
    

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25. Migration Plan
    1.All new dev work in Kotlin
    2.If anything larger than a small bug fix must be
    done to a class, consider migrating the class to
    Kotlin
    3.Start migrating existing code
    © @n8ebel, Udacity Engineering 2018 25
    

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26. Migration Plan
    Planned to tackle the low hanging fruit first
    (utilities, helpers, isolated classes)
    Work towards migrating enough code that the majority
    of our daily development would be in Kotlin
    © @n8ebel, Udacity Engineering 2018 26
    

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27. Migration Process
    » Started by using the Java to Kotlin conversion
    tool within Android Studio
    » Then made manual adjustments to the converted code
    © @n8ebel, Udacity Engineering 2018 27
    

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28. Migration Process
    Some of the adjustments we made to converted code:
    » Avoiding the use of !! operator
    » When possible, convert helper methods to top-level
    functions
    » Avoid companion object where possible
    » Reorganize the generated code
    » Expressing code in a more Kotlin idiomatic way
    © @n8ebel, Udacity Engineering 2018 28
    

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29. Handling null
    In many places we focused on leveraging statements
    such as
    object?.let {...}
    instead of
    if(object != null) { ... }
    © @n8ebel, Udacity Engineering 2018 29
    

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30. stdlib
    Tried to leverage the great collections stdlib that
    Kotlin provides.
    Allowed us to replace large blocks of code with a few
    lines of concise functional code
    © @n8ebel, Udacity Engineering 2018 30
    

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31. Shorter, safer code
    val recentQueries:List? = listOf()
    val recentsToDisplay = recentQueries
    ?.filterNotNull()
    ?.filter{ it.isNotBlank() }
    ?.take(5)
    ?: listOf()
    © @n8ebel, Udacity Engineering 2018 31
    

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32. Where Are We Today?
    © @n8ebel, Udacity Engineering 2018 32
    

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33. Flagship App
    Our flagship codebase continues to be migrated to
    Kotlin
    » ~40% Kotlin today
    » All new dev work is done in Kotlin
    © @n8ebel, Udacity Engineering 2018 33
    

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34. New Codebase
    Additional code base that is 100% Kotlin
    » Allowed us to fully explore the language
    » Have began using several language features
    extensively
    © @n8ebel, Udacity Engineering 2018 34
    

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35. New Codebase
    Began leveraging more interesting aspects of the
    language
    » data classes
    » sealed classes
    » named arguments & default parameter values
    » higher order functions
    © @n8ebel, Udacity Engineering 2018 35
    

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36. Tips for Incorporating Kotlin
    © @n8ebel, Udacity Engineering 2018 36
    

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37. Tips for Incorporating Kotlin
    » If new to the language, start with the conversion
    tool
    » Don’t be afraid to further modify the converted
    code
    © @n8ebel, Udacity Engineering 2018 37
    

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38. Tips for Incorporating Kotlin
    Start with tests
    - can help work out build issues
    - explore basic syntax
    - great for understanding interop story
    Features
    - writing feature code will give a more comprehensive
    picture of how it can affect your code
    © @n8ebel, Udacity Engineering 2018 38
    

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39. Tips for Incorporating Kotlin
    Don’t go wild trying to write “idiomatic” Kotlin.
    - As you progress with the language, it’s likely your
    opinion of whats readable vs what’s possible will
    evolve
    © @n8ebel, Udacity Engineering 2018 39
    

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40. “Just because you can doesn’t mean you should”
    © @n8ebel, Udacity Engineering 2018 40
    

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41. Tips for Incorporating Kotlin
    » As you migrate existing code, re-visit previously
    converted code from time to time. You may find
    that newly discovered conventions/patterns could
    be applied.
    » Don’t forget to thoroughly test any interop layers
    between Java and Kotlin. Nullability issues can
    crop up during runtime when dealing with nullable
    platform types.
    © @n8ebel, Udacity Engineering 2018 41
    

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42. “Explore, experiment, migrate, refactor”
    © @n8ebel, Udacity Engineering 2018 42
    

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43. How Can Kotlin Improve Your Product?
    take advantage of this period of exploration while
    learning the language
    © @n8ebel, Udacity Engineering 2018 43
    

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44. How Can Kotlin Improve Your Product?
    Question existing patterns/conventions for writing
    Android apps and ask yourself if/how Kotlin might
    enable you to write alternative solutions
    © @n8ebel, Udacity Engineering 2018 44
    

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45. How Can Kotlin Improve Your Product?
    » can your code be refactored to avoid null
    properties?
    » can you replace helper classes/methods with top-
    level functions?
    » can you avoid handling null properties by using a
    delegate?
    » could a logical path be expressed using functional
    concepts to reduce a class’s state?
    © @n8ebel, Udacity Engineering 2018 45
    

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46. Moving Forward
    © @n8ebel, Udacity Engineering 2018 46
    

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47. Confident Moving Forward
    We feel great about our investment into Kotlin
    » Google continues to poor resources into Kotlin
    » Samples now defaulting to Kotlin
    » New ktx library for Android
    » Increased interest from users will accelerate
    improvements
    © @n8ebel, Udacity Engineering 2018 47
    

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48. More From Udacity
    Free Course
    - Kotlin for Android Developers
    Engineering Blog Posts*
    - Adopting Kotlin
    - Learning Kotlin by Mistake
    - Modeling ViewModel States Using Kotlin’s Sealed
    Classes
    © @n8ebel, Udacity Engineering 2018 48
    

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