SHIPPING A MOBILE MULTIPLATFORM PROJECT ON IOS & ANDROID

Given by Ben Asher (@benasher44) and Alec Strong (@strongolopolis).
Video: https://youtu.be/je8aqW48JiA

Getting a multiplatform project started within an active engineering team across multiple platforms is challenging. You have to pitch the project to your colleagues, wrestle with reconciling platform-specific technical issues, and actually ship it for each supported platform.

We have spent the last year doing just that for PlanGrid and CashApp. Come learn how to get your multiplatform project started and what kinds of problems you can expect to solve along the way. We'll approach the problems from both the Android and iOS perspectives and arm you with the tools to make multiplatform not a multiproblem.

Transcript

1. Copenhagen Denmark SHIPPING MULTIPLATFORM ON IOS & ANDROID BEN ASHER ALEC STRONG @benasher44 @strongolopolis
2. Link to another sheet Markups
3. History
4. Live Info
5. Championed on iOS ~15 across Android and iOS Construction Championed on Android ~30 across Android and iOS Financial Services
6. Offline Sync System Search Business Logic
7. MPP Business Logic Models
8. MPP Business Logic Models
9. MPP
10. MPP Kotlin/Native
13. New tools New language Uneven ecosystem !!! !!!
14. Adopting cross-platform in your app has a cost
15. What is the value that makes it worth the effort?
16. Diverging Sync Systems
17. Existing Shared Code
18. What tools will your cross-platform solution need What is the common goal all stakeholders have
19. What else? No JNI on Android Obj-C
 Interop Not New For Android Community Jetbrains
20. Common Questions Kotlin/Native relies on Obj-C? What about Swift? Obj-C header is well-annotated for Swift This is the status quo for Apple’s own frameworks
21. Common Questions What about performance? Same performance expectations on Android Can drop into C if needed on iOS
22. Common Questions What about value types?
23. Common Questions There’s a garbage collector? But there’s no JVM, right? Bacon’s Algorithm for GC
24. Common Questions What libraries can we use for mpp? JVM Distributions are incomplete Special multiplatform distributions K/N ABI instability (klib)
25. Common Questions What is “common” code?
26. commonMain iosMain androidMain iOS - .framework Android - .aar Library Outputs Library Source Sets
27. commonMain iosMain androidMain iOS - .framework Android - .aar Library Outputs Library Source Sets Code expect class Lock actual class Lock actual class Lock
30. expect class Lock actual class Lock actual class Lock commonMain iosMain androidMain iOS - .framework Android - .aar Library Outputs Library Source Sets
31. commonMain iosMain androidMain iOS - .framework Android - .aar Library Outputs Library Source Sets
32. commonMain iosMain androidMain iOS - .framework Android - .aar Library Outputs Library Source Sets
33. commonMain iosMain androidMain iOS - .framework Android - .aar Library Outputs Library Source Sets windowsMain Windows - .dll
34. Is it platform agnostic? commonMain Yes No Will other common code use it? Yes No Platform
36. Is it platform agnostic? No Will other common code use it? commonMain Yes
37. expect class DatabaseFactory { internal fun createSqliteDriver(): SqlDriver }
38. Is it platform agnostic? No Will other common code use it? No Platform
39. sourceSets {A commonMain {B}C androidLibMain {D}E iosLibMain {F}G }H
40. sourceSets {A commonMain {B}C androidLibMain {D dependencies {I api project(‘:protos') }J }E iosLibMain {F}G }H
41. fun SearchQueries.insert(entity: SyncEntity) entity: SyncEntity
42. sourceSets {A commonMain {B}C androidLibMain {D}E iosLibMain {F}G }H
43. sourceSets {A commonMain {B}C androidLibMain {D}E }H
44. Is it platform agnostic? commonMain Yes
45. fun search(terms: String): List<Search>?
46. commonMain iosMain androidMain Library Source Sets Host
 Application
47. Host
 Application Talks to backend API Talks to existing application state
48. Host
 Application commonMain Library Initialization Library defines interface App provides implementation
50. Highly platform-specific Backend API Hosts Current user’s credential Case Study: Networking
51. Make an API request Receive an async response Interface can be re-implemented later MPP Life Hack: Interface Network
52. interface Network { /** * Makes an API request */ fun makeRequest( host: APIHost, request: Request, completion: (Request.Response) -> Unit ): NetworkDisposable }
53. interface Network { /** * Makes an API request */ fun makeRequest( host: APIHost, request: Request, completion: (Request.Response) -> Unit ): NetworkDisposable } host: APIHost Plain enum of names of the hosts– no URL handling required
54. interface Network { /** * Makes an API request */ fun makeRequest( host: APIHost, request: Request, completion: (Request.Response) -> Unit ): NetworkDisposable } request: Request data class: - String path and body, - query params dict - enum method (GET, POST, etc.)
55. interface Network { /** * Makes an API request */ fun makeRequest( host: APIHost, request: Request, completion: (Request.Response) -> Unit ): NetworkDisposable } completion: (Request.Response) -> Unit sealed class w/ different response types:
56. interface Network { /** * Makes an API request */ fun makeRequest( host: APIHost, request: Request, completion: (Request.Response) -> Unit ): NetworkDisposable } NetworkDisposable Interface with a cancel() method
57. suspend fun Network.makeRequest( host: APIHost, request: Request ): Request.Response
58. Concurrency in commonMain commonMain iosMain androidMain expect fun <T> T.freeze(): T actual fun <T> T.freeze(): T = this actual fun <T> T.freeze(): T = freeze()
61. Shipping Internally commonMain iosMain androidMain Host
 Application
62. commonMain iosMain androidMain Host
 Application Host
 Application
63. commonMain iosMain androidMain Host
 Application Host
 Application
64. Pros Cons Minimal change for android Seamless local development Single source of truth Host dependencies Two build environments for iOS CI Nightmare
65. commonMain iosMain androidMain Host
 Application Host
 Application commonMain
66. Pros Cons Minimal change for android Seamless local development Host dependencies Two build environments for iOS CI Nightmare for iOS Out of sync code
67. commonMain iosMain androidMain Host
 Application Host
 Application
68. Pros Cons CI is fast Encourages unit test coverage Single source of truth Breaking changes are painful Need good CD setup Debugging decoupled repos
69. commonMain iosMain Host
 Application Host
 Application androidMain
70. commonMain androidMain Host
 Application Host
 Application
71. Shipping Externally Test Crashing!
72. Shipping Externally fun crash() { (null as String?)!! }
73. Shipping Externally setUnhandledExceptionHook()
74. Shipping Externally What happens if a Worker crashes?
80. Define your project’s goals Be thoughtful growing your codebase Avoid solving general muliplatform problems Get your CI and dev setup working early Join us in Kotlin slack Review