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
2. THE TRIUMPHS AND TRIBULATIONS OF KOTLIN/NATIVE IN PRACTICE APPDEVCON | AMSTERDAM, NL | MARCH 2019 @DESIGNATEDNERD | BAKKENBAECK.NO | JUSTHUM.COM
6. !
7. !
16. THE VIRTUAL MACHINE
22. SHAMELESS PLUG! HTTPS://STORE.RAYWENDERLICH.COM PRODUCTS/KOTLIN-APPRENTICE
28. !
29. PACKAGE THIEF VS. GLITTER BOMB TRAP HTTPS://WWW.YOUTUBE.COM/WATCH?V=XOXHDK-HWUO
46. PACKAGE THIEF VS. GLITTER BOMB TRAP HTTPS://WWW.YOUTUBE.COM/WATCH?V=XOXHDK-HWUO
52. ! "
55. WITH WHAT SYSTEMS SHALL I BUILD IT?
57. Raspberry pi
58. Raspberry pi Server
59. Raspberry pi Server iOS app
60. Raspberry pi Server iOS app Android App
61. Works with Kotlin? Raspberry pi Server iOS app Android App
62. Works With Kotlin? Raspberry pi ✅ Server ✅ iOS app ✅ Android App ✅
63. HTTP://BAKKENBAECK.NO
64. HTTPS://GITHUB.COM/BAKKENBAECK/ PORCH PIRATE PROTECTOR
66. NATIVE VS. MULTI-PLATFORM
67. apply plugin: 'kotlin-multiplatform'
68. apply plugin: 'kotlin-native-platform' apply plugin: 'kotlin-multiplatform'
69. // For Native ONLY projects apply plugin: 'kotlin-native-platform' apply plugin: 'kotlin-multiplatform'
70. // For Native ONLY projects apply plugin: 'kotlin-native-platform' // For projects targeting multiple platforms, // for example JVM + Native + JS apply plugin: 'kotlin-multiplatform'
71. LEARN TO LOVE (TO HATE)
74. PROTIP: USE GRADLE 4.10.1* enableFeaturePreview('GRADLE_METADATA')
75. PROTIP: USE GRADLE 4.10.1* enableFeaturePreview('GRADLE_METADATA') *as of March 15, 2018
78. GET READY TO CARE ABOUT FOLDER STRUCTURE
82. FUNCTIONS WITH PER-PLATFORM IMPLEMENTATIONS expect fun
88. CALLING CODE FROM BOTH APPS!
89. ANDROID: EASY MODE build.gradle SomeFragment.kt
90. IOS: MODE
96. ! OBJECTIVE-C
99. IOS/OBJC GOTCHAS
100. SWIFT Array != KOTLIN Array
101. SWIFT Array<T> == KOTLIN List<T>
102. SWIFT enum != KOTLIN enum class IN OBJC
103. KOTLIN enum class DayOfWeek { Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday; }
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") } }
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") }
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") }
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") }
109. DECIDING WHAT TO CENTRALIZE
110. WHAT DO I REALLY HATE BUILDING TWICE?
111. TALKING TO THE SERVER
112. JSON FROM NETWORK IN MODELS ⬅ JSON OUT TO NETWORK
118. IosClientEngine.kt https://github.com/ktorio/ktor/blob/master/ ktor-client/ktor-client-ios/darwin/src/io/ ktor/client/engine/ios/IosClientEngine.kt
119. ANDROID
120. IOS
121. IOS
123. ! FREEZING
125. TRY TO AVOID MUTATING VARIABLES
126. AVOID object FROM IOS
127. USE INTERFACES TO MUTATE THINGS IN IOS INSTEAD OF K/N
128. KOTLIN interface SecureStorage { fun storeTokenString(token: String) fun clearTokenString() fun fetchTokenString(): String? }
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 } }
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 } }
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 } }
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 } }
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() } }
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() } }
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() } }
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 } }
138. KotlinX Serialization
139. KOTLIN data class UserCredentials( val username: String, val password: String )
140. KOTLIN apply plugin: 'kotlinx-serialization' @Serializable data class UserCredentials( val username: String, val password: String )
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"
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"
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"
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"
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"
146. FROM CLIENT TO SERVER AND BACK!
147. LOGIC
148. MVC!
149. MVVM!
150. MVA!*
151. MVA!* * - ANYTHING OTHER THAN A MODEL OR A VIEW FOR THE LOVE OF GOD
152. MVP!
153. HTTPS://GITHUB.COM/JETBRAINS/ KOTLINCONF-APP
154. MODEL: VIEW: PRESENTER:
155. MODEL: data class VIEW: PRESENTER:
156. MODEL: data class VIEW: interface PRESENTER:
157. MODEL: data class VIEW: interface PRESENTER: class
158. VIEW: interface
159. IOS VIEW: ANDROID VIEW: TESTING VIEW:
160. IOS VIEW: UIViewController ANDROID VIEW: TESTING VIEW:
161. IOS VIEW: UIViewController ANDROID VIEW: Fragment* TESTING VIEW:
162. IOS VIEW: UIViewController ANDROID VIEW: Fragment* TESTING VIEW: *May not apply if your name is jake wharton
163. IOS VIEW: UIViewController ANDROID VIEW: Fragment* TESTING VIEW: ¯\_(ϑ)_/¯ *May not apply if your name is jake wharton
164. KOTLIN/NATIVE
165. KOTLIN/NATIVE
166. KOTLIN/NATIVE
167. KOTLIN/NATIVE
168. KOTLIN/NATIVE
169. ANDROID
170. ANDROID
171. IOS
172. IOS
173. TESTING YOUR COMMON CODE
174. commonTest WORKS IF COROUTINES AREN'T INVOLVED!
179. runBlocking DOESN'T EXIST FOR KOTLIN/NATIVE
180. ANYTHING WITH COROUTINES MUST BE TESTED ON THE JVM
181. androidTest WILL ALSO RUN YOUR commonTest TESTS!
184. THINGS YOU'LL LEARN DOING SERVER DEVELOPMENT
185. THINGS YOU'LL LEARN DOING SERVER DEVELOPMENT (WHICH HAVE LITTLE TO NOTHING TO DO WITH KOTLIN)
186. THINGS YOU'LL LEARN DOING SERVER DEVELOPMENT > Docker
187. THINGS YOU'LL LEARN DOING SERVER DEVELOPMENT > Docker > MySQL
188. THINGS YOU'LL LEARN DOING SERVER DEVELOPMENT > Docker > MySQL > ORMs for MySQL
189. THINGS YOU'LL LEARN DOING SERVER DEVELOPMENT > Docker > MySQL > ORMs for MySQL > One-way hashing for secure password storage
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
195. DO WE HAVE TIME FOR A TERRIBLE IDEA?
196. AND NOW, A TERRIBLE IDEA: A LIVE DEMO!
197. !"# NEXT STEPS
198. !"# NEXT STEPS > Build the prototype box
199. !"# NEXT STEPS > Build the prototype box > Get the Raspberry pi software working
200. !"# NEXT STEPS > Build the prototype box > Get the Raspberry pi software working > Get the raspberry pi actually unlocking the box
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
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
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?
204. OBLIGATORY SUMMARY SLIDE!
205. OBLIGATORY SUMMARY SLIDE! > Kotlin/Native has made great strides in the last year
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
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
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
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
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
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