Magic and Tricks with Kotlin Multiplatform

This talk is for mobile engineers that have experience with Swift or Kotlin for iOS and Android We will cover the getting started guide for all the developers that are interested in moving to Kotlin Multiplatform as a production-ready tool, taking into consideration all the pitfalls and advantages we can have using it, we will cover some simple clever things you can do with Ktor and SQLiteDelight to simplify modularization, take advantages of Serialization, and the terrific world of Kotlin Multiplatform. Talking about how to shape your architecture for a production app, and sharing your architecture, without leaving behind the OS, the security and the performance of your app, sometimes we forgot that for a good production app we need a good architecture that is testable, that is taking consideration of concurrency and databases.

Transcript

1. Magic and tricks: with
   Kotlin Multiplatform
   Dinorah Tovar
   Unidos compartiendo y aprendiendo
   #SGVirtual
   

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2. DISCLAIMER!
   

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3. KOTLIN

   IS COOL
   

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4. KOTLIN MULTIPLATFORM 

   IS COOLER
   

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5. KOTLIN IS A JVM LANGUAGE,
   NOT AN ANDROID LANGUAGE
   

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6. WHAT THE HECK IS KMP?
   

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7. TRY IT BEFORE YOU BUY IT
   FULL OPTIONAL
   

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8. SHARING CODE
   

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9. SO, IS CROSS-PLATFORM? OR A
   FRAMEWORK
   KINDA CROSS
   

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10. ONLY LOGIC, NO UI
    

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11. ONLY LOGIC, “NO UI”
    

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13. SO, WHAT THE HECK IS? IS A
    FRAMEWORK? A SDK? A PLUGIN?
    

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14. “Kotlin's philosophy is that you don't have to migrate the entire application.
    Start from a easy place”

    

    -Jetbrains
    IS A SDK!
    

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15. SHARED BUSINESS LOGIC
    

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16. SHARED BUSINESS LOGIC
    • Not restrictions
    •Appearance and behavior is the same
    •Performance is fully Native!
    

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17. ANDROID AND IOS ARE KINDA THE SAME, RIGHT?
    •They are “Unix like”
    •They have multithreading operations
    •They have file/primitive saving of data and pretty
    much, they use SQL
    

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18. HOW DOES IT WORK?
    

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19. KOTLIN MULTIPLATFORM
    Kotlin 

    Compiler
    Kotlin

    Multiplatform
    Native JS JVM
    JAR/AAR (For Android)
    JS (For React or Node)
    Binaries (For iOS)
    

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20. KOTLIN MULTIPLATFORM
    

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21. KOTLIN MULTIPLATFORM
    sourceSets {
    commonMain {
    dependencies {
    api project(":common-all")
    implementation 'org.jetbrains.kotlin:kotlin-stdlib-common'
    ---
    }
    }
    commonTest {
    dependencies {
    implementation "org.jetbrains.kotlin:kotlin-test-common"
    ---
    }
    }
    androidMain {
    dependsOn commonMain
    dependencies {
    

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22. commonTest {
    dependencies {
    implementation "org.jetbrains.kotlin:kotlin-test-common"
    ---
    }
    }
    androidMain {
    dependsOn commonMain
    dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    ---
    }
    }
    iOSMain {
    dependsOn commonMain
    dependencies {
    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core-native:
    $coroutines_version"
    ----
    }
    }
    }
    KOTLIN MULTIPLATFORM
    

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23. I DON’T GET IT, SHARING
    CODE? HOW?
    

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24. KOTLIN MULTIPLATFORM
    •Use a Plugin in your grade to configure your “blocks”
    •We configure a Kotlin block, with our targets! One for
    Android and one for iOS
    

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25. KOTLIN MULTIPLATFORM
    

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26. EXAMPLE
    •The most primitive way to save a primitive variable in
    Android and iOS is: SharedPreferences and
    NSUserDefaults
    

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27. EXAMPLE
    •The most primitive way to save a primitive variable in
    Android and iOS is: SharedPreferences and
    NSUserDefaults
    •Kotlin only knows how to compile Kotlin code into
    different targets but you can make Kotlin aware of
    this by using the expect/actual mechanism.
    

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28. SAVING VALUES
    //Common Code
    expect fun saveValueLocally(value: String)
    //Android Code
    actual fun saveValueLocally(value: String) {
    //Create shared preferences
    sharedPreferences.edit { putString("Value", value) }
    }
    //iOS Code
    actual fun saveValueLocally(value: String) {
    NSUserDefaults.standardUserDefaults.setValue(
    value,
    forKey = "Value"
    )
    }
    

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29. MULTITHREADING
    

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30. SAY HI TO KTOR!
    Ktor
    Kotlin
    Serialization
    Coroutines
    Retrofit
    Kotlin
    Serialization
    Coroutines
    /RxJava
    Alamofire
    RxSwift/
    Composite
    Decode/
    Encode/
    etc…
    

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31. HTTP CLIENT
    // commonMain
    expect val engine: HttpClientEngine
    // androidMain
    actual val engine by lazy { Android.create() }
    // iosMain
    actual val engine by lazy { Ios.create() }
    

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32. HTTP CLIENT
    class GetDogsRepository {
    private val client = HttpClient(engine) {
    install(JsonFeature) {
    serializer = KotlinxSerializer().apply {
    register(Dogs.serializer().list)
    }
    }
    }
    suspend fun getDogs(): List =
    client.get("https://www.dogs.com.mx/isleofdogs")
    }
    

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33. COROUTINES SUPPORT!
    expect open class MyViewModel() {
    val clientScope: CoroutineScope
    protected open fun onCleared()
    }
    actual open class MyViewModel actual constructor(): ViewModel()
    

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34. COROUTINES SUPPORT FOR IOS… KINDA
    Coroutines
    Hot
    Streams
    Cold
    Streams
    

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35. COROUTINES SUPPORT FOR IOS… KINDA
    actual open class MyViewModel actual constructor() {
    private val viewModelJob = SupervisorJob()
    val viewModelScope: CoroutineScope = CoroutineScope(IosMainDispatcher + viewModelJob)
    actual val clientScope: CoroutineScope = viewModelScope
    protected actual open fun onCleared() {
    viewModelJob.cancelChildren()
    }
    object IosMainDispatcher : CoroutineDispatcher() {
    override fun dispatch(context: CoroutineContext, block: Runnable) {
    dispatch_async(dispatch_get_main_queue()) { block.run() }
    }
    }
    }
    

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36. OKIO AND OKHTTP
    

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37. OKIO AND OKHTTP
    

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38. DATABASES
    

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39. SAY HI TO SQLITEDELIGHT!
    •Databases are hard!
    •SQLDelight generates typesafe APIs from your SQL
    statements
    •Android and iOS use SQL
    

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40. SAY HI TO SQLITEDELIGHT!
    CREATE TABLE dogs (
    dogName TEXT NOT NULL,
    dogRace TEXT NOT NULL
    );
    

    insert:
    INSERT INTO dogs (dogName, dogRace)
    VALUES ('Spots', 'Best friend');
    

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41. FULL SUPPORT FOR IOS AND ANDROID
    class DogsDao(database: Dogs) {
    private val db = database.dogsModelQueries
    internal fun insert(item: Dogs) {
    db.insertItem(
    dogName = item.dogName,
    dogRace = item.dogRace
    )
    }
    internal fun select():List = db.selectAll().executeAsList()
    }
    

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42. FIREBASE
    

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43. FIREBASE PLUGIN
    

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44. GRAPHQL
    

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45. APOLLO FOR MULTIPLATFORM
    •Apollo queries can be really complicated
    •One wrong detail in the query and there will be
    nothing in the tree to search
    

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46. APOLLO FOR MULTIPLATFORM
    

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47. APOLLO FOR MULTIPLATFORM
    •Apollo Runtime [Android]
    •Apollo API [iOS]
    •You can now add your schema.json and other
    graphql files under src/commonMain/graphql
    

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48. THE REAL QUESTION?, IS
    READY FOR PROD?
    

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49. WAIT FOR THE FUTURE
    

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50. Magic and tricks: with
    Kotlin Multiplatform
    Unidos compartiendo y aprendiendo
    #SGVirtual
    Dinorah Tovar
    Lead Mobile Engineer
    @ddinorahtovar
    @ddinorahtovar
    @dinorahto
    @dinorahto
    

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