Refactoring to Kotlin - Kotlin/Everywhere

Wajahat Karim delivers a talk about refactoring to Kotlin at Kotlin/Everywhere event organized by Android Pakistan Community (https://www.androidpakistancommunity.com/).

Full video of the talk is available at: https://www.youtube.com/watch?v=ciof7IiRAKw

Transcript

1. Refactoring to Kotlin
   Wajahat Karim
   Moving Big Old Java Codebase to New Awesome Kotlin
   WajahatKarim
   

   View Slide

2. I am Wajahat Karim
   And I work at Contour Software.
   Hey There!
   Coding
   8+ Years Experienced
   Android Developer
   Writing
   Authored 2 Worldwide
   Published Books
   Passion
   Open Source Contributor
   (many Android libraries)
   Community
   AndroidPub, FlutterPub,
   Articles, and Talks
   

   View Slide

3. This is a story of...
   

   View Slide

4. Messy Code
   Deprecated Libraries
   Frustrated Developers
   Not-so-happy Clients
   And Project X
   

   View Slide

5. An Uber-like app for businesses (B2B)
   73+ screens and counting
   6+ different apps for each customer with own colors, server, features
   400+ classes (including Activity, Views, Models, POJOs)
   Existing codebase to work upon - Code modification takes double time.
   Project X
   

   View Slide

6. What We Expected
   Modern APIs & Frameworks
   Some good architecture like MVP, MVVM etc.
   Well organized & commented code
   Unit & Instrumentation Tests
   

   View Slide

7. What We Got
   Modern APIs & Frameworks - 2010 codebase never upgraded in years
   Some good architecture like MVP, MVVM etc. - Everything is in one BIG class.
   Well organized & commented code - Who has time for it?
   Unit & Instrumentation Tests - Sorry? What’s that? Never heard of it before.
   

   View Slide

8. Old Code Architecture
   

   View Slide

9. Let’s convert it Kotlin...
   CTRL + SHIFT + K
   

   View Slide

10. View Slide

11. New Code Architecture
    

    View Slide

12. Refactor vs Rewrite
    No disturbance in existing features
    New features & bug fixes
    Tight deadlines & less time
    Too big risk to handle
    Refactoring
    

    View Slide

13. What We Did
    1. Move all network code to Network Repository
    2. Move all local persistence code to Local Repository
    3. Move everything except UI, Navigation, & Business Logic to Common / Utils
    4. Create separate Activity/Fragment from big multiple-screen classes
    5. Integrate Kotlin & MVVM Core classes
    6. Move Business Logic to ViewModel
    

    View Slide

14. 1. Unit & Instrumentation Testing
    2. CI/CD Automation
    3. Integrate Room database
    4. Integrate Retrofit + Coroutines
    What’s Next
    

    View Slide

15. Show’em the code!
    

    View Slide

16. Kotlin Extensions = ❤
    https://wajahatkarim.com/2019/03/-launching-activities-in-easier-way-using-kotlin-extensions-
    

    View Slide

17. Domain Specific Language (DSL)
    Java
    Kotlin with DSL Builder
    https://android.jlelse.eu/domain-specific-language-dsl-using-kotlin-with-retrofit-example-9be5ef65a4fb
    

    View Slide

18. @JVMStatic
    Kotlin
    Without @JVMStatic in Java
    With @JVMStatic in Java
    

    View Slide

19. https://wajahatkarim.com wajahatkarim3@gmail.com
    github.com/wajahatkarim3 @WajahatKarim
    Any Questions?
    medium.com/@wajahatkarim3
    

    View Slide