The Triumphs and Tribulations of Kotlin/Native In Practice - AppDevCon, Amsterdam, Netherlands - March 2019

First talk about a project I've been working on with K/N!

Abstract:
The promise of write-once-run-everywhere has haunted native mobile developers since the first time someone whispered the words “phone gap”. But what if there was a way to have cross-platform development with a modern, type-safe language? JetBrains is trying to make this happen with Kotlin/Native, which compiles to LLVM bytecode, and can run on iOS, Android, and even the web. Learn more about some of the benefits of working with Kotlin/Native, some of the drawbacks, and a few of the (current) potential dealbreakers when it comes to using this exciting new technology in a real app.

Links:
- Main Project: https://github.com/bakkenbaeck/PorchPirateProtector
- Initial K/N Test: https://github.com/designatednerd/KotlinNativeTest

Transcript

1. THE TRIUMPHS AND TRIBULATIONS
   OF KOTLIN/NATIVE IN PRACTICE
   APPDEVCON | AMSTERDAM, NL | MARCH 2019
   @DESIGNATEDNERD | BAKKENBAECK.NO | JUSTHUM.COM
   

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2. THE TRIUMPHS AND TRIBULATIONS
   OF KOTLIN/NATIVE IN PRACTICE
   APPDEVCON | AMSTERDAM, NL | MARCH 2019
   @DESIGNATEDNERD | BAKKENBAECK.NO | JUSTHUM.COM
   

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6. !
   

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7. !
   

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16. THE
    VIRTUAL MACHINE
    

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22. SHAMELESS PLUG!
    HTTPS://STORE.RAYWENDERLICH.COM
    PRODUCTS/KOTLIN-APPRENTICE
    

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28. !
    

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29. PACKAGE THIEF
    VS.
    GLITTER BOMB TRAP
    HTTPS://WWW.YOUTUBE.COM/WATCH?V=XOXHDK-HWUO
    

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46. PACKAGE THIEF
    VS.
    GLITTER BOMB TRAP
    HTTPS://WWW.YOUTUBE.COM/WATCH?V=XOXHDK-HWUO
    

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52. ! "
    

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55. WITH WHAT SYSTEMS
    SHALL I BUILD IT?
    

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57. Raspberry pi
    

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58. Raspberry pi
    Server
    

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59. Raspberry pi
    Server
    iOS app
    

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60. Raspberry pi
    Server
    iOS app
    Android App
    

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61. Works with Kotlin?
    Raspberry pi
    Server
    iOS app
    Android App
    

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62. Works With Kotlin?
    Raspberry pi ✅
    Server ✅
    iOS app ✅
    Android App ✅
    

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63. HTTP://BAKKENBAECK.NO
    

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64. HTTPS://GITHUB.COM/BAKKENBAECK/
    PORCH PIRATE PROTECTOR
    

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66. NATIVE VS. MULTI-PLATFORM
    

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67. apply plugin: 'kotlin-multiplatform'
    

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68. apply plugin: 'kotlin-native-platform'
    apply plugin: 'kotlin-multiplatform'
    

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69. // For Native ONLY projects
    apply plugin: 'kotlin-native-platform'
    apply plugin: 'kotlin-multiplatform'
    

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70. // For Native ONLY projects
    apply plugin: 'kotlin-native-platform'
    // For projects targeting multiple platforms,
    // for example JVM + Native + JS
    apply plugin: 'kotlin-multiplatform'
    

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71. LEARN TO LOVE (TO HATE)
    

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74. PROTIP: USE GRADLE 4.10.1*
    enableFeaturePreview('GRADLE_METADATA')
    

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75. PROTIP: USE GRADLE 4.10.1*
    enableFeaturePreview('GRADLE_METADATA')
    *as of March 15, 2018
    

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76. View Slide

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78. GET READY TO CARE ABOUT
    FOLDER STRUCTURE
    

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82. FUNCTIONS WITH PER-PLATFORM IMPLEMENTATIONS
    expect fun
    

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88. CALLING CODE FROM
    BOTH APPS!
    

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89. ANDROID: EASY MODE
    build.gradle
    SomeFragment.kt
    

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90. IOS: MODE
    

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96. !
    OBJECTIVE-C
    

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99. IOS/OBJC GOTCHAS
    

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100. SWIFT Array != KOTLIN Array
     

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101. SWIFT Array == KOTLIN List
     

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102. SWIFT enum != KOTLIN enum class IN OBJC
     

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103. KOTLIN
     enum class DayOfWeek {
     Monday,
     Tuesday,
     Wednesday,
     Thursday,
     Friday,
     Saturday,
     Sunday;
     }
     

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104. KOTLIN
     fun printForDay(day: DayOfWeek) {
     when (day) {
     DayOfWeek.Monday -> println("You can fall apart")
     DayOfWeek.Tuesday,
     DayOfWeek.Wednesday -> println("Break my heart")
     DayOfWeek.Thursday -> println("Doesn't even start")
     DayOfWeek.Friday -> println("I'm in love")
     DayOfWeek.Saturday -> println("Wait")
     DayOfWeek.Sunday -> print("Always comes too late")
     }
     }
     

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106. SWIFT
     func printForDay(_ day: DayOfWeek) {
     switch day {
     case .monday:
     print("You can fall apart")
     case .tuesday,
     .wednesday:
     print("Break my heart")
     case .thursday:
     print("Doesn't even start")
     case .friday:
     print("I'm in love")
     case .saturday:
     print("Wait")
     case .sunday:
     print("Always comes too late")
     default:
     fatalError("Not a day")
     }
     

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107. SWIFT
     func printForDay(_ day: DayOfWeek) {
     switch day {
     case .monday:
     print("You can fall apart")
     case .tuesday,
     .wednesday:
     print("Break my heart")
     case .thursday:
     print("Doesn't even start")
     case .friday:
     print("I'm in love")
     case .saturday:
     print("Wait")
     case .sunday:
     print("Always comes too late")
     default:
     fatalError("Not a day")
     }
     

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108. SWIFT
     func printForDay(_ day: DayOfWeek) {
     switch day {
     case .monday:
     print("You can fall apart")
     case .tuesday,
     .wednesday:
     print("Break my heart")
     case .thursday:
     print("Doesn't even start")
     case .friday:
     print("I'm in love")
     case .saturday:
     print("Wait")
     case .sunday:
     print("Always comes too late")
     default: // <-
     ! ! !
     fatalError("Not a day")
     }
     

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109. DECIDING WHAT TO
     CENTRALIZE
     

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110. WHAT DO I REALLY HATE
     BUILDING TWICE?
     

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111. TALKING TO THE SERVER
     

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112. JSON FROM NETWORK IN
     MODELS
     ⬅
     JSON OUT TO NETWORK
     

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118. IosClientEngine.kt
     https://github.com/ktorio/ktor/blob/master/
     ktor-client/ktor-client-ios/darwin/src/io/
     ktor/client/engine/ios/IosClientEngine.kt
     

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119. ANDROID
     

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120. IOS
     

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121. IOS
     

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123. !
     FREEZING
     

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125. TRY TO AVOID MUTATING VARIABLES
     

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126. AVOID object FROM IOS
     

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127. USE INTERFACES
     TO MUTATE THINGS IN IOS INSTEAD OF K/N
     

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128. KOTLIN
     interface SecureStorage {
     fun storeTokenString(token: String)
     fun clearTokenString()
     fun fetchTokenString(): String?
     }
     

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129. SWIFT
     @objc class Keychain: NSObject, SecureStorage {
     static let shared = Keychain()
     private override init() {
     super.init()
     }
     //TODO: Actually use keychain
     private var token: String?
     func storeTokenString(token: String) {
     self.token = token
     }
     func clearTokenString() {
     self.token = nil
     }
     func fetchTokenString() -> String? {
     return self.token
     }
     }
     

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130. SWIFT
     @objc class Keychain: NSObject, SecureStorage {
     static let shared = Keychain()
     private override init() {
     super.init()
     }
     //TODO: Actually use keychain
     private var token: String?
     func storeTokenString(token: String) {
     self.token = token
     }
     func clearTokenString() {
     self.token = nil
     }
     func fetchTokenString() -> String? {
     return self.token
     }
     }
     

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131. SWIFT
     @objc class Keychain: NSObject, SecureStorage {
     static let shared = Keychain()
     private override init() {
     super.init()
     }
     //TODO: Actually use keychain
     private var token: String?
     func storeTokenString(token: String) {
     self.token = token
     }
     func clearTokenString() {
     self.token = nil
     }
     func fetchTokenString() -> String? {
     return self.token
     }
     }
     

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132. SWIFT
     @objc class Keychain: NSObject, SecureStorage {
     static let shared = Keychain()
     private override init() {
     super.init()
     }
     //TODO: Actually use keychain
     private var token: String?
     func storeTokenString(token: String) {
     self.token = token
     }
     func clearTokenString() {
     self.token = nil
     }
     func fetchTokenString() -> String? {
     return self.token
     }
     }
     

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133. KOTLIN
     object TokenManager {
     fun currentToken(storage: SecureStorage): UserToken? {
     storage.fetchTokenString()?.let {
     return UserToken(it)
     } ?: return null
     }
     fun storeToken(token: UserToken, storage: SecureStorage) {
     storage.storeTokenString(token.token)
     }
     fun clearToken(storage: SecureStorage) {
     storage.clearTokenString()
     }
     }
     

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134. KOTLIN
     object TokenManager {
     fun currentToken(storage: SecureStorage): UserToken? {
     storage.fetchTokenString()?.let {
     return UserToken(it)
     } ?: return null
     }
     fun storeToken(token: UserToken, storage: SecureStorage) {
     storage.storeTokenString(token.token)
     }
     fun clearToken(storage: SecureStorage) {
     storage.clearTokenString()
     }
     }
     

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135. KOTLIN
     object TokenManager {
     fun currentToken(storage: SecureStorage): UserToken? {
     storage.fetchTokenString()?.let {
     return UserToken(it)
     } ?: return null
     }
     fun storeToken(token: UserToken, storage: SecureStorage) {
     storage.storeTokenString(token.token)
     }
     fun clearToken(storage: SecureStorage) {
     storage.clearTokenString()
     }
     }
     

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136. SWIFT
     @objc class Keychain: NSObject, SecureStorage {
     static let shared = Keychain()
     private override init() {
     super.init()
     }
     //TODO: Actually use keychain
     private var token: String?
     func storeTokenString(token: String) {
     self.token = token
     }
     func clearTokenString() {
     self.token = nil
     }
     func fetchTokenString() -> String? {
     return self.token
     }
     }
     

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138. KotlinX Serialization
     

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139. KOTLIN
     data class UserCredentials(
     val username: String,
     val password: String
     )
     

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140. KOTLIN
     apply plugin: 'kotlinx-serialization'
     @Serializable
     data class UserCredentials(
     val username: String,
     val password: String
     )
     

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141. KOTLIN
     val creds = UserCredentials("lol@ha.no", "guessme")
     val string = Json.stringify(UserCredentials.serializer(), creds)
     // String is '{"username":"lol@ha.no","password":"guessme"}'
     val updatedCreds = Json.parse(UserCredentials.serializer(), string)
     // updatedCreds.username is "lol@ha.no"
     // updatedCreds.password is "guessme"
     

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142. KOTLIN
     val creds = UserCredentials("lol@ha.no", "guessme")
     val string = Json.stringify(UserCredentials.serializer(), creds)
     // String is '{"username":"lol@ha.no","password":"guessme"}'
     val updatedCreds = Json.parse(UserCredentials.serializer(), string)
     // updatedCreds.username is "lol@ha.no"
     // updatedCreds.password is "guessme"
     

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143. KOTLIN
     val creds = UserCredentials("lol@ha.no", "guessme")
     val string = Json.stringify(UserCredentials.serializer(), creds)
     // String is '{"username":"lol@ha.no","password":"guessme"}'
     val updatedCreds = Json.parse(UserCredentials.serializer(), string)
     // updatedCreds.username is "lol@ha.no"
     // updatedCreds.password is "guessme"
     

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144. KOTLIN
     val creds = UserCredentials("lol@ha.no", "guessme")
     val string = Json.stringify(UserCredentials.serializer(), creds)
     // String is '{"username":"lol@ha.no","password":"guessme"}'
     val updatedCreds = Json.parse(UserCredentials.serializer(), string)
     // updatedCreds.username is "lol@ha.no"
     // updatedCreds.password is "guessme"
     

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145. KOTLIN
     val creds = UserCredentials("lol@ha.no", "guessme")
     val string = Json.stringify(UserCredentials.serializer(), creds)
     // String is '{"username":"lol@ha.no","password":"guessme"}'
     val updatedCreds = Json.parse(UserCredentials.serializer(), string)
     // updatedCreds.username is "lol@ha.no"
     // updatedCreds.password is "guessme"
     

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146. FROM CLIENT TO SERVER AND BACK!
     

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147. LOGIC
     

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148. MVC!
     

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149. MVVM!
     

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150. MVA!*
     

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151. MVA!*
     * - ANYTHING OTHER THAN A MODEL OR A VIEW FOR THE LOVE OF GOD
     

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152. MVP!
     

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153. HTTPS://GITHUB.COM/JETBRAINS/
     KOTLINCONF-APP
     

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154. MODEL:
     VIEW:
     PRESENTER:
     

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155. MODEL: data class
     VIEW:
     PRESENTER:
     

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156. MODEL: data class
     VIEW: interface
     PRESENTER:
     

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157. MODEL: data class
     VIEW: interface
     PRESENTER: class
     

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158. VIEW: interface
     

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159. IOS VIEW:
     ANDROID VIEW:
     TESTING VIEW:
     

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160. IOS VIEW: UIViewController
     ANDROID VIEW:
     TESTING VIEW:
     

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161. IOS VIEW: UIViewController
     ANDROID VIEW: Fragment*
     TESTING VIEW:
     

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162. IOS VIEW: UIViewController
     ANDROID VIEW: Fragment*
     TESTING VIEW:
     *May not apply if your name is jake wharton
     

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163. IOS VIEW: UIViewController
     ANDROID VIEW: Fragment*
     TESTING VIEW: ¯\_(ϑ)_/¯
     *May not apply if your name is jake wharton
     

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164. KOTLIN/NATIVE
     

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165. KOTLIN/NATIVE
     

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166. KOTLIN/NATIVE
     

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167. KOTLIN/NATIVE
     

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168. KOTLIN/NATIVE
     

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169. ANDROID
     

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170. ANDROID
     

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171. IOS
     

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172. IOS
     

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173. TESTING YOUR COMMON CODE
     

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174. commonTest
     WORKS IF COROUTINES AREN'T INVOLVED!
     

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179. runBlocking
     DOESN'T EXIST FOR KOTLIN/NATIVE
     

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180. ANYTHING WITH COROUTINES MUST BE TESTED
     ON THE JVM
     

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181. androidTest
     WILL ALSO RUN YOUR commonTest TESTS!
     

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184. THINGS YOU'LL LEARN DOING
     SERVER DEVELOPMENT
     

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185. THINGS YOU'LL LEARN DOING
     SERVER DEVELOPMENT
     (WHICH HAVE LITTLE TO NOTHING TO DO WITH KOTLIN)
     

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186. THINGS YOU'LL LEARN DOING SERVER DEVELOPMENT
     > Docker
     

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187. THINGS YOU'LL LEARN DOING SERVER DEVELOPMENT
     > Docker
     > MySQL
     

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188. THINGS YOU'LL LEARN DOING SERVER DEVELOPMENT
     > Docker
     > MySQL
     > ORMs for MySQL
     

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189. THINGS YOU'LL LEARN DOING SERVER DEVELOPMENT
     > Docker
     > MySQL
     > ORMs for MySQL
     > One-way hashing for secure password storage
     

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190. THINGS YOU'LL LEARN DOING SERVER DEVELOPMENT
     > Docker
     > MySQL
     > ORMs for MySQL
     > One-way hashing for secure password storage
     > Your computer's exact melting point
     

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195. DO WE HAVE TIME FOR
     A TERRIBLE IDEA?
     

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196. AND NOW, A TERRIBLE IDEA:
     A LIVE DEMO!
     

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197. !"#
     NEXT STEPS
     

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198. !"#
     NEXT STEPS
     > Build the prototype box
     

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199. !"#
     NEXT STEPS
     > Build the prototype box
     > Get the Raspberry pi software working
     

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200. !"#
     NEXT STEPS
     > Build the prototype box
     > Get the Raspberry pi software working
     > Get the raspberry pi actually unlocking the box
     

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201. !"#
     NEXT STEPS
     > Build the prototype box
     > Get the Raspberry pi software working
     > Get the raspberry pi actually unlocking the box
     > Work on sharing design elements
     

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202. !"#
     NEXT STEPS
     > Build the prototype box
     > Get the Raspberry pi software working
     > Get the raspberry pi actually unlocking the box
     > Work on sharing design elements
     > Work on sharing localized strings
     

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203. !"#
     NEXT STEPS
     > Build the prototype box
     > Get the Raspberry pi software working
     > Get the raspberry pi actually unlocking the box
     > Work on sharing design elements
     > Work on sharing localized strings
     > Maybe find someone who knows what they're doing to
     build it for real?
     

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204. OBLIGATORY SUMMARY SLIDE!
     

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205. OBLIGATORY SUMMARY SLIDE!
     > Kotlin/Native has made great strides in the last year
     

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206. OBLIGATORY SUMMARY SLIDE!
     > Kotlin/Native has made great strides in the last year
     > Share logic across iOS, android, and server without
     killing performance or sacrificing type/null safety
     

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207. OBLIGATORY SUMMARY SLIDE!
     > Kotlin/Native has made great strides in the last year
     > Share logic across iOS, android, and server without
     killing performance or sacrificing type/null safety
     > it's still beta, You will run into a lot of brick walls
     

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208. OBLIGATORY SUMMARY SLIDE!
     > Kotlin/Native has made great strides in the last year
     > Share logic across iOS, android, and server without
     killing performance or sacrificing type/null safety
     > it's still beta, You will run into a lot of brick walls
     > Ktor and kotlinX serialization are a huge help, if you
     can get around what a mess coroutines can be on iOS
     

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209. OBLIGATORY SUMMARY SLIDE!
     > Kotlin/Native has made great strides in the last year
     > Share logic across iOS, android, and server without
     killing performance or sacrificing type/null safety
     > it's still beta, You will run into a lot of brick walls
     > Ktor and kotlinX serialization are a huge help, if you
     can get around what a mess coroutines can be on iOS
     > This is experimental, but it's stupid amounts of fun
     

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210. View Slide

211. LINKS!
     > Kotlin MPP for iOS + Android tutorial
     https://kotlinlang.org/docs/tutorials/
     native/mpp-ios-android.html
     > KotlinConf App
     https://github.com/JetBrains/kotlinconf-
     app
     > KotlinLang Slack
     https://slack.kotlinlang.org
     

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212. LINKS!
     > My original Kotlin Native sandbox
     https://github.com/designatednerd/
     KotlinNativeTest
     > Package Thief vs. Glitter Bomb Trap
     https://youtube.com/watch?v=xoxhDk-hwuo
     

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