Sharing [Kotlin code across platforms] is caring!

Sharing code across platforms is one of the most annoying "unsolved problems" when developing a product: an eternal struggle between re-writing everything multiple times and jumping through plenty of hoops to be able to re-use some core business logic. This session is going to illustrate how Kotlin is being used to solve this problem at Clue in order to share code between Android, iOS and the backend, including all the challenges, lessons and tricks learned along the way.

Presented at KotlinConf 2017

Transcript

1. @workingkills
   Eugenio Marletti
   Sharing
   [Kotlin code across platforms]
   is caring!
   KotlinConf
   

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2. “app”
   “ ”
   “ ”
   “ ”
   “ ”
   

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3. “app”
   iOS
   Android
   frontend
   backend
   tools
   “ ”
   “ ”
   “ ”
   “ ”
   

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4. sharing
   

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5. code
   sharing
   

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6. code
   sharing
   

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7. business logic
   sharing
   

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8. bugs
   sharing
   

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9. bugs
   sharing
   

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10. fixes
    sharing
    

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11. effort
    sharing
    

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12. C++
    J2ObjC / GWT
    JavaScript
    

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14. THE ALGORITHM™
    

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15. THE ALGORITHM™
    C++
    ObjC++
    JavaScript
    TypeScript
    

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16. C++
    ObjC++
    JavaScript
    TypeScript
    iOS !" JavaScriptCore
    Android !" WebView
    

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17. C++
    ObjC++
    JavaScript
    TypeScript
    iOS !" JavaScriptCore
    Android !" W
    ͊̊̏̃͑̽̃̕
    ̘͖̯
    㸅
    ̨͇̯
    ̶ȩ̧̟̝͔
    ͔͎̗̬̼̓̒̄̍̓͐̒̎̕
    b̡̫̰͙͚͋͋̓́̇͟V
    ͐̇͞ ̓̿̔̿̓ ͒̚
    ͟ ̨̭̳̱͕
    ̵i
    ͒̅̉͊̌̇
    ̡͓̰̲̳͟ ̥̯
    ̯̦ę͕͔͉̜̗͔͎
    ̔̍̀̏̌̕
    ͢ ͟
    w
    ̛͊͆̍͑
    ̴̯̯̻̪̦
    

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18. ?
    C++
    ObjC++
    JavaScript
    TypeScript
    iOS !" JavaScriptCore
    Android !"
    

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19. THE ALGORITHM™
    C++
    ObjC++
    JavaScript
    TypeScript
    Kotlin @fbecart
    Florent Bécart
    

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20. multi-platform
    

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21. header impl
    (before 1.2)
    -Xmulti-platform
    

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22. header impl
    (before 1.2)
    -Xmulti-platform
    

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23. expect actual
    (from 1.2)
    -Xmulti-platform
    

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24. ANDROID
    WebView
    iOS
    JavaScriptCore
    BACKEND
    JS
    legacy.js
    

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25. legacy-test.js
    ANDROID
    WebView
    iOS
    JavaScriptCore
    BACKEND
    JS
    legacy.js
    shared-test.kt
    shared.kt
    

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26. legacy-test.js
    ANDROID
    WebView
    iOS
    JavaScriptCore
    BACKEND
    JS
    legacy.js
    shared-test.kt
    shared.kt
    

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27. legacy-test.js
    ANDROID
    WebView
    iOS
    JavaScriptCore
    BACKEND
    JS
    legacy.js
    shared-test.kt
    shared.kt
    

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28. legacy-test.js
    ANDROID
    WebView
    iOS
    JavaScriptCore
    BACKEND
    JS
    legacy.js
    shared.kt
    shared-test.kt
    

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29. legacy-test.js
    ANDROID
    WebView
    iOS
    JavaScriptCore
    BACKEND
    JS
    shared.kt
    shared-test.kt
    JVM
    

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30. /**
    * A day number, offset from 01/01/2012
    !"
    export type Day = number
    

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31. /**
    * A day number, offset from 01/01/2012
    !"
    typealias Day = Int
    

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32. class Value {
    constructor(value: Double) {
    this.value = value
    }
    val value: Double
    override fun toString(): String {
    return this.value.toString()
    }
    companion object {
    fun add(v1: Value, v2: Value): Value {
    return Value(v1.value + v2.value)
    }
    fun isZero(valueWithVariance: Value): Boolean {
    return .0 !!% valueWithVariance.value
    }
    fun subtract(v1: Value?, v2: Value?): Value {
    var value = .0
    if (v1 !' null !& v2 !' null) { value = v1.value - v2.value }
    return Value(value)
    }
    }
    }
    export class Value {
    constructor(value) {
    this.value = value
    }
    readonly value: number
    toString() {
    return String(this.value)
    }
    static add = (v1: Value, v2: Value): Value !$ {
    return new Value(v1.value + v2.value)
    }
    static isZero = (valueWithVariance: Value): boolean !$ {
    return 0 !!% valueWithVariance.value
    }
    static subtract = (v1: Value, v2: Value): Value !$ {
    let value = 0
    if (v1 !& v2) { value = v1.value - v2.value }
    return new Value(value)
    }
    }
    

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33. < insert more talking here >
    

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34. Eugenio
    Marletti
    @workingkills
    BIT.LY/SHARING-KOTLIN-IS-CARING
    

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