Building Multiplatform projects with Kotlin (TechTrain 2018)

Kotlin was presented as a better Java and eventually it could not skip the Write Once Run Everywhere concept, but did this in its own way. The other day we got an ability to build multiplatform applications in Kotlin - it doesn't try to make us write everything under JVM and run the result on different platforms using virtual machine. On the contrary, our code will be compiled for each platform separately and it's not advised to unite platform-specific functionality in any way. But our business logic, on the other hand, is the right thing to be shared and written only once.

In this talk we'll explore Kotlin's concept of multiplatform projects and dissect its features using an example of Android application and browser extension with common code.

Video: https://youtu.be/MWV5TS2gNzU

Transcript

1. Building Multiplatform Projects with Kotlin Sergey Ryabov
7. WRITE ONCE, RUN EVERYWHERE! © JAVA
8. Client Backend Models Business Logic Presenters Views Android
9. Client Backend Models Business Logic Presenters Views Android Client Backend Models Business Logic Presenters Views iOS Client Backend Models Business Logic Presenters Views Web Models Business Logic Backend
10. Client Backend Models Business Logic Presenters Views Android Client Backend Business Logic Presenters Views iOS Client Backend Business Logic Presenters Views Web Business Logic Backend
11. Client Backend Models Business Logic Presenters Views Android Client Backend Presenters Views iOS Client Backend Presenters Views Web Business Logic Backend
12. Client Backend Models Business Logic Presenters Views Android Client Backend Views iOS Client Backend Views Web Business Logic Backend
13. WHAT DO WE ALREADY HAVE FOR THAT?
14. • C++ WHAT DO WE ALREADY HAVE FOR THAT?
15. • C++ • J2ObjC + GWT WHAT DO WE ALREADY HAVE FOR THAT?
16. • C++ • J2ObjC + GWT • Xamarin WHAT DO WE ALREADY HAVE FOR THAT?
17. • C++ • J2ObjC + GWT • Xamarin • ReactNative / Flutter WHAT DO WE ALREADY HAVE FOR THAT?
18. MAJOR PROBLEMS
19. • Access to native APIs MAJOR PROBLEMS
20. • Access to native APIs • Latest SDK version support MAJOR PROBLEMS
21. • Access to native APIs • Latest SDK version support • Modern dev stack MAJOR PROBLEMS
22. • Access to native APIs • Latest SDK version support • Modern dev stack • Executable size MAJOR PROBLEMS
23. WHY KOTLIN?
24. Feb 2016 - Kotlin 1.0: production JVM, experimental JS WHY KOTLIN?
25. Feb 2016 - Kotlin 1.0: production JVM, experimental JS Mar 2017 - Kotlin 1.1: production JS WHY KOTLIN?
26. Feb 2016 - Kotlin 1.0: production JVM, experimental JS Mar 2017 - Kotlin 1.1: production JS Apr 2017 - Kotlin Native Tech Preview WHY KOTLIN?
27. Feb 2016 - Kotlin 1.0: production JVM, experimental JS Mar 2017 - Kotlin 1.1: production JS Apr 2017 - Kotlin Native Tech Preview Nov 2017 - Kotlin Native 0.4: iOS support WHY KOTLIN?
28. Feb 2016 - Kotlin 1.0: production JVM, experimental JS Mar 2017 - Kotlin 1.1: production JS Apr 2017 - Kotlin Native Tech Preview Nov 2017 - Kotlin Native 0.4: iOS support Nov 2017 - Kotlin 1.2: Multiplatform projects, JVM/JS support WHY KOTLIN?
29. Feb 2016 - Kotlin 1.0: production JVM, experimental JS Mar 2017 - Kotlin 1.1: production JS Apr 2017 - Kotlin Native Tech Preview Nov 2017 - Kotlin Native 0.4: iOS support Nov 2017 - Kotlin 1.2: Multiplatform projects, JVM/JS support Feb 2018 - Kotlin Native 0.6: Multiplatform support WHY KOTLIN?
30. Feb 2016 - Kotlin 1.0: production JVM, experimental JS Mar 2017 - Kotlin 1.1: production JS Apr 2017 - Kotlin Native Tech Preview Nov 2017 - Kotlin Native 0.4: iOS support Nov 2017 - Kotlin 1.2: Multiplatform projects, JVM/JS support Feb 2018 - Kotlin Native 0.6: Multiplatform support + transparent ObjC/Kotlin collection types interop WHY KOTLIN?
31. Feb 2016 - Kotlin 1.0: production JVM, experimental JS Mar 2017 - Kotlin 1.1: production JS Apr 2017 - Kotlin Native Tech Preview Nov 2017 - Kotlin Native 0.4: iOS support Nov 2017 - Kotlin 1.2: Multiplatform projects, JVM/JS support Feb 2018 - Kotlin Native 0.6: Multiplatform support + transparent ObjC/Kotlin collection types interop Jul 2018 - Kotlin Native 0.8: kotlin-stdlib sync with JVM/JS WHY KOTLIN?
32. WHY KOTLIN IS BETTER?
33. WHY KOTLIN IS BETTER? • Access to native APIs
34. WHY KOTLIN IS BETTER? • Access to native APIs • Latest SDK version support
35. WHY KOTLIN IS BETTER? • Access to native APIs • Latest SDK version support • Modern dev stack
36. WHY KOTLIN IS BETTER? • Access to native APIs • Latest SDK version support • Modern dev stack • Executable size
37. HOW DOES IT WORK IN KOTLIN?
38. • Gradle multimodule projects HOW DOES IT WORK IN KOTLIN?
39. • Gradle multimodule projects • Common HOW DOES IT WORK IN KOTLIN?
40. • Gradle multimodule projects • Common • Platform HOW DOES IT WORK IN KOTLIN?
41. • Gradle multimodule projects • Common • Platform • Regular
 HOW DOES IT WORK IN KOTLIN?
42. • Gradle multimodule projects • Common • Platform • Regular
 • Multiplatform headers & implementations HOW DOES IT WORK IN KOTLIN?
43. • Gradle multimodule projects • Common • Platform • Regular
 • Multiplatform headers & implementations • expect & actual HOW DOES IT WORK IN KOTLIN?
44. Models Presenters Business Logic Views Repository
45. Models Presenters Business Logic Views Repository
46. Models common Presenters Business Logic common-client Views Repository
47. Models common common-client Presenters Business Logic View Interfaces Repo Interfaces Repository Views
48. Models common common-client Presenters Business Logic View Interfaces Repo Interfaces JS Models common-js JVM Models common-jvm Repository Repository Views Views Views
49. Models common common-client Presenters Business Logic View Interfaces Repo Interfaces Repository Views client-js JS Models common-js JVM Models common-jvm Repository Views client-android Views
50. Models common common-client Presenters Business Logic View Interfaces Repo Interfaces Repository Views client-js Repository client-jvm JS Models common-js JVM Models common-jvm Views client-android Views client-desktop
51. Models common common-client Presenters Business Logic View Interfaces Repo Interfaces Repository Views client-js Repository client-jvm JS Models common-js JVM Models common-jvm backend Views client-android Views client-desktop
52. EXAMPLE: ANDROID APP + FIREFOX EXTENSION
53. EXAMPLE: ANDROID APP + FIREFOX EXTENSION http://jennift.com/dpical.html Original
54. EXAMPLE: ANDROID APP + FIREFOX EXTENSION http://jennift.com/dpical.html Original
55. Business Logic View Interfaces common android Views Views js EXAMPLE: ANDROID APP + FIREFOX EXTENSION Presenters
56. CAVEATS
57. • Drawbacks of the concept CAVEATS
58. • Drawbacks of the concept • Lots of manual work for module configuration (KT-23930) CAVEATS
59. • Drawbacks of the concept • Lots of manual work for module configuration (KT-23930) • Several platform codebases can’t sit in one module (different SourceSets )
 CAVEATS
60. • Drawbacks of the concept • Lots of manual work for module configuration (KT-23930) • Several platform codebases can’t sit in one module (different SourceSets )
 • Every platform has its own problems CAVEATS
61. • Drawbacks of the concept • Lots of manual work for module configuration (KT-23930) • Several platform codebases can’t sit in one module (different SourceSets )
 • Every platform has its own problems • Kotlin/JS CAVEATS
62. • Drawbacks of the concept • Lots of manual work for module configuration (KT-23930) • Several platform codebases can’t sit in one module (different SourceSets )
 • Every platform has its own problems • Kotlin/JS • One output JS-file per module CAVEATS
63. • Drawbacks of the concept • Lots of manual work for module configuration (KT-23930) • Several platform codebases can’t sit in one module (different SourceSets )
 • Every platform has its own problems • Kotlin/JS • One output JS-file per module • Manual setup for including libs in the output CAVEATS
64. • Drawbacks of the concept • Lots of manual work for module configuration (KT-23930) • Several platform codebases can’t sit in one module (different SourceSets )
 • Every platform has its own problems • Kotlin/JS • One output JS-file per module • Manual setup for including libs in the output • Kotlin/Native CAVEATS
65. • Drawbacks of the concept • Lots of manual work for module configuration (KT-23930) • Several platform codebases can’t sit in one module (different SourceSets )
 • Every platform has its own problems • Kotlin/JS • One output JS-file per module • Manual setup for including libs in the output • Kotlin/Native • Still experimental - some features are not supported CAVEATS
66. • Drawbacks of the concept • Lots of manual work for module configuration (KT-23930) • Several platform codebases can’t sit in one module (different SourceSets )
 • Every platform has its own problems • Kotlin/JS • One output JS-file per module • Manual setup for including libs in the output • Kotlin/Native • Still experimental - some features are not supported • No reuse for multiplatform (yet) CAVEATS
67. FUTURE PLANS
68. • Re-thinking Multimodule projects configuration FUTURE PLANS
69. • Re-thinking Multimodule projects configuration • Catching up Kotlin/Native with other platforms FUTURE PLANS
70. • Re-thinking Multimodule projects configuration • Catching up Kotlin/Native with other platforms • Increasing common libs count • kotlin.test • kotlinx.html • kotlinx.serialization • kotlinx.coroutines • kotlinx.io • SQLDelight • … FUTURE PLANS
71. PRODUCTION USAGE
72. • KotlinConf app (https://github.com/jetbrains/kotlinconf-app) PRODUCTION USAGE
73. • KotlinConf app (https://github.com/jetbrains/kotlinconf-app) • Droidcon NYC (Sessionize) app (https://github.com/touchlab/DroidconKotlin) PRODUCTION USAGE
74. • KotlinConf app (https://github.com/jetbrains/kotlinconf-app) • Droidcon NYC (Sessionize) app (https://github.com/touchlab/DroidconKotlin) • Revolut (in-progress) PRODUCTION USAGE
75. WRITE ONCE,.RUN EVERYWHERE
76. WRITE ONCE,.SHARE EVERYWHERE
77. • Create common business logic, not UI WRITE ONCE,.SHARE EVERYWHERE
78. • Create common business logic, not UI • Write every part of the app in one language (optional) WRITE ONCE,.SHARE EVERYWHERE
79. • Code from the talk https://goo.gl/VYgHmr • Serialization support for Kotlin/Native https://github.com/Kotlin/kotlinx.serialization/issues/86 • Channels support for Kotlin/Native https://github.com/Kotlin/kotlinx.coroutines/issues/462 • New Multiplatform configuration approach https://youtrack.jetbrains.com/issue/KT-23930 LINKS
80. Building Multiplatform Projects with Kotlin Sergey Ryabov @colriot