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Copenhagen
Denmark
SHIPPING
MULTIPLATFORM ON
IOS & ANDROID
BEN ASHER
ALEC STRONG
@benasher44 @strongolopolis
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Link to
another sheet
Markups
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History
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Live Info
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Championed on iOS
~15 across Android and iOS
Construction
Championed on Android
~30 across Android and iOS
Financial Services
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Offline
Sync System
Search
Business Logic
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MPP
Business Logic
Models
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MPP
Business Logic
Models
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MPP
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MPP
Kotlin/Native
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New tools
New language
Uneven ecosystem
!!!
!!!
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Adopting cross-platform in your app has a cost
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What is the value that makes it worth the effort?
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Diverging Sync Systems
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Existing Shared Code
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What tools will your cross-platform solution need
What is the common goal all stakeholders have
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What else?
No JNI
on Android
Obj-C
Interop
Not New
For Android
Community
Jetbrains
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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
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Common Questions
What about performance?
Same performance expectations on Android
Can drop into C if needed on iOS
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Common Questions
What about value types?
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Common Questions
There’s a garbage collector? But there’s no JVM, right?
Bacon’s Algorithm for GC
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Common Questions
What libraries can we use for mpp?
JVM Distributions are incomplete
Special multiplatform distributions
K/N ABI instability (klib)
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Common Questions
What is “common” code?
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commonMain
iosMain
androidMain
iOS - .framework
Android - .aar
Library Outputs Library Source Sets
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commonMain
iosMain
androidMain
iOS - .framework
Android - .aar
Library Outputs Library Source Sets Code
expect class Lock
actual class Lock
actual class Lock
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expect class Lock
actual class Lock
actual class Lock
commonMain
iosMain
androidMain
iOS - .framework
Android - .aar
Library Outputs Library Source Sets
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commonMain
iosMain
androidMain
iOS - .framework
Android - .aar
Library Outputs Library Source Sets
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commonMain
iosMain
androidMain
iOS - .framework
Android - .aar
Library Outputs Library Source Sets
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commonMain
iosMain
androidMain
iOS - .framework
Android - .aar
Library Outputs Library Source Sets
windowsMain
Windows - .dll
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Is it platform agnostic?
commonMain
Yes
No Will other common
code use it?
Yes
No
Platform
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Is it platform agnostic?
No Will other common
code use it?
commonMain
Yes
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expect class DatabaseFactory {
internal fun createSqliteDriver(): SqlDriver
}
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Is it platform agnostic?
No Will other common
code use it?
No
Platform
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sourceSets {A
commonMain {B}C
androidLibMain {D}E
iosLibMain {F}G
}H
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sourceSets {A
commonMain {B}C
androidLibMain {D
dependencies {I
api project(‘:protos')
}J
}E
iosLibMain {F}G
}H
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fun SearchQueries.insert(entity: SyncEntity)
entity: SyncEntity
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sourceSets {A
commonMain {B}C
androidLibMain {D}E
iosLibMain {F}G
}H
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sourceSets {A
commonMain {B}C
androidLibMain {D}E
}H
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Is it platform agnostic?
commonMain
Yes
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fun search(terms: String): List?
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commonMain
iosMain
androidMain
Library Source Sets
Host
Application
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Host
Application
Talks to backend API
Talks to existing application state
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Host
Application
commonMain
Library Initialization
Library defines interface
App provides implementation
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Highly platform-specific
Backend API Hosts
Current user’s credential
Case Study: Networking
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Make an API request
Receive an async response
Interface can be re-implemented later
MPP Life Hack: Interface Network
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interface Network {
/**
* Makes an API request
*/
fun makeRequest(
host: APIHost,
request: Request,
completion: (Request.Response) -> Unit
): NetworkDisposable
}
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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
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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.)
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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:
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interface Network {
/**
* Makes an API request
*/
fun makeRequest(
host: APIHost,
request: Request,
completion: (Request.Response) -> Unit
): NetworkDisposable
}
NetworkDisposable
Interface with a cancel() method
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suspend fun Network.makeRequest(
host: APIHost,
request: Request
): Request.Response
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Concurrency in commonMain
commonMain
iosMain
androidMain
expect fun T.freeze(): T
actual fun T.freeze(): T = this
actual fun T.freeze(): T = freeze()
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Shipping Internally
commonMain
iosMain
androidMain
Host
Application
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commonMain
iosMain
androidMain
Host
Application
Host
Application
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commonMain
iosMain
androidMain
Host
Application
Host
Application
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Pros Cons
Minimal change for android
Seamless local development
Single source of truth
Host dependencies
Two build environments for iOS
CI Nightmare
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commonMain
iosMain
androidMain
Host
Application
Host
Application
commonMain
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Pros Cons
Minimal change for android
Seamless local development
Host dependencies
Two build environments for iOS
CI Nightmare for iOS
Out of sync code
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commonMain
iosMain
androidMain
Host
Application
Host
Application
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Pros Cons
CI is fast
Encourages unit test coverage
Single source of truth
Breaking changes are painful
Need good CD setup
Debugging decoupled repos
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commonMain
iosMain
Host
Application
Host
Application
androidMain
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commonMain
androidMain
Host
Application
Host
Application
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Shipping Externally
Test Crashing!
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Shipping Externally
fun crash() {
(null as String?)!!
}
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Shipping Externally
setUnhandledExceptionHook()
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Shipping Externally
What happens if a Worker crashes?
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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