10 Reasons To Try Kotlin Multiplatform [GOTO Copenhagen edition]

Is multiplatform development a realistic proposition? What should drive you to choose Kotlin Multiplatform over the alternatives? In this talk, I’ll take a close look at the Kotlin Multiplatform technology and ecosystem and offer ten compelling reasons why you should give it a go!

Those in the know will surely be aware that the Kotlin ecosystem has been transforming. Thanks to new compilers, libraries, and frameworks, Kotlin has become a multiplatform environment. You can develop compelling apps on the desktop, iOS, Android, and even WebAssembly – all from a single codebase. As such, Kotlin Multiplatform is now in direct competition with technologies like Flutter and React Native.

Transcript

2. 10 Reasons To Try Kotlin Multiplatform Pamela Hill Developer Advocate - JetBrains
3. Kotlin Multiplatform is a technology by JetBrains
4. Kotlin Multiplatform allows development teams to share common code between platforms
5. • Server • Mobile • Desktop • Web What kind of platforms?
6. Kotlin Multiplatform is currently in Beta, and going to Stable soon 🎉
7. 1. Already used by big companies
8. #1: Already used by big companies
9. #1: Already used by big companies
10. #1: Already used by big companies
11. #1: Already used by big companies
12. kotl.in/kmp-case-studies #1: Already used by big companies
13. 2. Extensive list of supported platforms 1. Already used by big companies
14. What kind of platforms? Server Android iOS Desktop Web Kotlin Multiplatform WASM JS #2: Extensive list of supported platforms
15. What is WASM? • WebAssembly (WASM) is a binary instruction format for portable virtual machines • Smaller, faster than JavaScript • Don’t write code in WASM, but languages like Kotlin / Go / Rust, compile to WASM • Already supported in most modern browsers, Node.js #2: Extensive list of supported platforms
16. The story of Quizlet https://kotlinlang.org/lp/multiplatform/case-studies/quizlet/ #2: Extensive list of supported platforms
17. Tried other technologies https://kotlinlang.org/lp/multiplatform/case-studies/quizlet/ • JavaScript • React Native • C++/Rust/Go #2: Extensive list of supported platforms
18. Settled on Kotlin Multiplatform 🏆 Android iOS Web Kotlin Multiplatform https://kotlinlang.org/lp/multiplatform/case-studies/quizlet/ #2: Extensive list of supported platforms
19. The results 🏆 ✅ Type-safe APIs when marshalling objects ✅ Performance on Android/iOS improved ✅ Android app size decreased ✅ Better developer experience ✅ Different team members keen to try writing shared code #2: Extensive list of supported platforms
20. Another scenario: sharing code between clients/server #2: Extensive list of supported platforms
21. Before: Sharing data models Use a language-neutral, platform-neutral language like Protocol Buffers ✅ Use with any language - like Go 🚫 Need to learn yet another format 🚫 Need to generate data classes from .proto files on all platforms #2: Extensive list of supported platforms
22. Sharing data models with Kotlin Multiplatform 🏆 ✅ Use a familiar language with great tooling ✅ Write once, use everywhere ❓Does it work with all your languages (server-side: only JVM) #2: Extensive list of supported platforms
23. 3. Supportive community 1. Already used by big companies 2. Extensive list of supported platforms
24. Kotlinlang Slack Workspace • 56k+ members • Relevant channels: ◦ #multiplatform ◦ #compose-ios • Q&A with JetBrains/Google/other knowledgeable experts #3: Supportive community
25. #3: Supportive community
26. Google @Google Touchlab @TouchlabHQ Philipp Lackner @plcoding John O’Reilly @joreilly Sebastian Aigner @sebi_io Garth Gilmour @GarthGilmour Lena Stepanova @hlnstep Tadeas Kriz @TadeasKriz #3: Supportive community
27. 4. Avoid duplication 2. Extensive list of supported platforms 3. Supportive community
28. The story of Wonder by Baidu https://kotlinlang.org/lp/multiplatform/case-studies/baidu #4: Avoid duplication
29. The problem with native app dev https://kotlinlang.org/lp/multiplatform/case-studies/baidu • Inconsistencies in the app experience • High cost of verifying the business logic • High upgrade and maintenance costs #4: Avoid duplication
30. “The complex and inconsistent business logic of the iOS and Android platforms led to increasing maintenance costs for the app.” - Baidu #4: Avoid duplication
31. Unifying data layer https://kotlinlang.org/lp/multiplatform/case-studies/baidu • Data model • RESTful API requests • JSON data parsing • Caching logic #4: Avoid duplication
32. Adopting MVI to unify interface logic https://kotlinlang.org/lp/multiplatform/case-studies/baidu • Low-level data • Processing logic • UI processing logic #4: Avoid duplication
33. The results 🏆 ✅ Consistent experience ✅ Reduced cost of maintenance ✅ Reduced cost of testing ✅ Improved productivity https://kotlinlang.org/lp/multiplatform/case-studies/baidu #4: Avoid duplication
34. 5. Use in new or existing projects 3. Supportive community 4. Avoid duplication
35. Existing projects: The example of Wonder by Baidu https://kotlinlang.org/lp/multiplatform/case-studies/baidu #5: Use in new or existing projects
36. New projects: The story of 9GAG https://raymondctc.medium.com/adopting-kotlin-multiplatform-mobile-kmm-on-9gag-app-dfe526d9ce04 #5: Use in new or existing projects
37. Tried other technologies https://raymondctc.medium.com/adopting-kotlin-multiplatform-mobile-kmm-on-9gag-app-dfe526d9ce04 • React Native (2016) • Flutter (2020) #5: Use in new or existing projects
38. Settled on Kotlin Multiplatform (2021) https://raymondctc.medium.com/adopting-kotlin-multiplatform-mobile-kmm-on-9gag-app-dfe526d9ce04 • Start from Android • Consume Kotlin Multiplatform project as dependency on iOS #5: Use in new or existing projects
39. 6. Start sharing gradually 4. Avoid duplication 5. Use in new or existing projects
40. Start small • Constants • Migrate common utilities • Write or migrate business logic #6: Start sharing gradually
41. #8: Start sharing gradually
42. 7. Choose what to share, what to write natively 5. Use in new or existing projects 6. Start sharing gradually
43. Before Kotlin Multiplatform Business / Domain (Entities, Use Cases, Interactors) Data / Core (Repositories, HTTP Clients, Cache) UI (Views) Presentation (Presenters, View Models, Controllers) iOS Business / Domain (Entities, Use Cases, Interactors) Data / Core (Repositories, HTTP Clients, Cache) UI (Views) Presentation (Presenters, View Models, Controllers) Android Business / Domain (Entities, Use Cases, Interactors) Data / Core (Repositories, HTTP Clients, Cache) UI (Views) Presentation (Presenters, View Models, Controllers) Desktop #7: Choose what to share, what to write natively
44. Sharing Business Logic Business / Domain (Entities, Use Cases, Interactors) Data / Core (Repositories, HTTP Clients, Cache) UI (Views) Presentation (Presenters, View Models, Controllers) iOS Kotlin Multiplatform Shared Module UI (Views) Presentation (Presenters, View Models, Controllers) Android UI (Views) Presentation (Presenters, View Models, Controllers) Desktop #7: Choose what to share, what to write natively
45. Sharing UI Logic Business / Domain (Entities, Use Cases, Interactors) Data / Core (Repositories, HTTP Clients, Cache) UI (Views) iOS Kotlin Multiplatform Shared Module UI (Views) Android UI (Views) Presentation (Presenters, View Models, Controllers) Desktop #7: Choose what to share, what to write natively
46. With ✨ Compose Multiplatform✨ Business / Domain (Entities, Use Cases, Interactors) Data / Core (Repositories, HTTP Clients, Cache) iOS Kotlin Multiplatform Shared Module UI (Views) Android Presentation (Presenters, View Models, Controllers) Desktop Platform-specific code Platform-specific code Platform-specific code #7: Choose what to share, what to write natively
47. 8. Share UI code 5. Use in new or existing projects 6. Choose what to share, what to write natively
48. https://developer.android.com/jetpack/compose #8: Share UI code
49. https://jb.gg/compose #8: Share UI code
50. State of platforms Android iOS Desktop WASM Compose Multiplatform Stable Alpha Stable Experimental #8: Share UI code
51. Official Sample - ImageViewer App #8: Share UI code
52. Community Sample - NY Times App https://www.github.com/xxfast/NYTimes-KMP #8: Share UI code
53. Finally, modern desktop development framework! #8: Share UI code
54. Code break 😅 #8: Share UI code
55. What did we see? ✅ Lots of code sharing between Android and iOS ✅ Using native code from common code ✅ Using common code from platform apps #8: Share UI code
56. 9. Comparable to native 7. Choose what to share, what to write natively 8. Share UI code
57. Using native dependencies • Support for Apple APIs - out of the box • Support for dependencies published as CocoaPods - tiny bit of configuration • Support for dependencies not managed by Dependency Manager - possible ➔ Makes the common easy, and the less common possible. #9: Comparable to native
58. No reasonable use cases known to be significantly less performant than native / other cross-platform #9: Comparable to native
59. ➔ Open to feedback #9: Comparable to native
60. 10. Kotlin is a loved & trusted language for everyone 🩷 8. Share UI code 9. Comparable to native
61. What do people say about Kotlin? • Concise • Expressive • Original • Sound https://www.youtube.com/watch?v=PsaFVLr8t4E (2018) #10. Because Kotlin
62. Kotlin aims to be pragmatic • Readability over concision • Reuse over expressiveness • Interoperability over originality • Safety & tooling over soundness https://www.youtube.com/watch?v=PsaFVLr8t4E (2018) #10. Because Kotlin
63. Kotlin is designed to make developers happier 😊 #10. Because Kotlin
64. #10. Because Kotlin
65. Makes developers more productive 😊 https://kotlinlang.org/docs/android-overview.html (2023) #10. Because Kotlin
66. Data Classes data class Person( val firstName: String, val secondName: String?, val surname: String ) {} • Getters, setters for each property • equals • hashCode • toString • copy • componentN #10. Because Kotlin
67. Fewer crashes 😊 https://medium.com/androiddevelopers/fewer-crashes-and-more-stability-with-kotlin-b606c6a6ac04 (2020) #10. Because Kotlin
68. Safely Handle null // Task 0: Print the name (naive) println("$firstName $secondName $surname") Adele Blue Adkins Taylor null Swift #10. Because Kotlin
69. Safely Handle null // Task 1: Print the second name in uppercase println("$firstName ${secondName?.uppercase()} $surname") Adele BLUE Adkins Taylor null Swift #10. Because Kotlin
70. Safely Handle null // Task 2: Println the second name in uppercase, if available println("$firstName ${secondName?.uppercase() ?: ""} $surname") Adele BLUE Adkins Taylor Swift #10. Because Kotlin
71. Improves safety, correctness 😊 https://medium.com/androiddevelopers/fewer-crashes-and-more-stability-with-kotlin-b606c6a6ac04 (2020) #10. Because Kotlin
72. Handling Equality Better Java // Value/Structural Equality person1.equals(person2) // Referential Equality person1 == person2 Kotlin // Value/Structural Equality person1 == person2 // Referential Equality person1 === person2 #10. Because Kotlin
73. “To == or not to ==, that is the question” - Java Hamlet #10. Because Kotlin
74. Where is Kotlin used?
75. #10. Because Kotlin
76. 95% Of top 1000 apps on Google Play use Kotlin #10. Because Kotlin
77. 23% Of top 1000 apps on Google Play use Jetpack Compose #10. Because Kotlin
78. Kotlin Web Frameworks https://kotlinlang.org/lp/server-side/ #10. Because Kotlin
79. Perhaps I’ve convinced you, what’s next?
80. Start small • Constants • A small shared irritation • Some common utilities
81. Work out an experiment plan 󰟾󰞲 • Hypothesis: what do we think will happen? • Method: how will we go about our experiment? • Conclusion: how will we analyse our results?
82. Work out an experiment plan 󰟾󰞲 • Team roles - who will contribute actively? • Workflow - how do you make, distribute changes? • Coding standards - how to write nice APIs • CI/CD - testing and rolling out • Monitoring production
83. Gain trust, expand the scope • Retrospective - did this really work for us? • Yes - do we want to expand the scope? • No - why?
84. Summary 1. Already used by big companies 2. Extensive list of supported platforms 3. Supportive community 4. Avoid duplication 5. Use in new or existing projects
85. 6. Start sharing gradually 7. Choose what to share, what to write natively 8. Share UI code 9. Comparable to native 10. Kotlin is a loved & trusted language for everyone Summary
86. 1. Start small 2. Work out an experiment plan 3. Gain trust, then expand the scope Summary - call to action
87. Questions? 🖐
88. Thank you! 🩷 Stay in touch: 𝕏 - @pamelaahill 📧 - pamela.hill@jetbrains.com 󰟲 - pamelaahill.com