Bridging the gap between Kotlin and Swift

Tooling and technologies around Kotlin Multiplatform always leave Apple platforms a little overboard. After all, Kotlin is a part of Android development, not in iOS. I will tell you what we do to fix it. You will learn about the Kotlin Multiplatform Mobile plugin for AppCode, what it was created for, and what it can do at the moment. I will show the latest developments in the Kotlin Multiplatform, and will tell you how they work from the inside.

Transcript

1. Aydar Mukhametzyanov, JetBrains Bridging the gap between Kotlin and Swift
2. Agenda New technologies in tooling for Kotlin Multiplatform Mobile Memory model and concurrency in Kotlin/Native 2
3. About me 2012 2019 iOS 2GIS, Freeletics… JetBrains AppCode 3
4. Kotlin Multiplatform Mobile 4
5. KMM plugin for Android Studio + Run | Debug | Test iOS 5
6. Problems of iOS development 6 KMM plugin for Android Studio
7. Shared.framework ⌨ New code ⏳ Build project 7 Problems of iOS development KMM plugin for Android Studio
8. class MyClass { fun hello() = "Hello from Kotlin!" } class MyClass { fun hello() = "Hello from Kotlin!" } 8 let a = MyClass() Problems of iOS development KMM plugin for Android Studio
9. 9 / / . . . _ _ attribute __ ((swift_name("KotlinDouble"))) @interface KNFDouble : KNFNumber - (instancetype)initWithDouble:(double)value; + (instancetype)numberWithDouble:(double)value; @end; _ _ attribute __ ((swift_name("KotlinBoolean"))) @interface KNFBoolean : KNFNumber - (instancetype)initWithBool:(BOOL)value; + (instancetype)numberWithBool:(BOOL)value; @end; _ _ attribute __ ((objc_subclassing_restricted)) _ _ attribute __ ((swift_name("MyClass"))) @interface KNFMyClass : KNFBase - (instancetype)init _ _ attribute __ ((swift_name("init()"))) __ attribute __ ((objc_designated_initializer)); + (instancetype)new __ attribute _ _ ((availability(swift, unavailable, message="use object initializers instead"))); - (NSString *)hello __ attribute _ _ ((swift_name("hello()"))); @end; Problems of iOS development KMM plugin for Android Studio
10. 10 Cmd+Shift+F Problems of iOS development KMM plugin for Android Studio
11. 11 • Lack of Swift and Obj-C support in Android Studio • Necessity to rebuild the framework every time you change the interface • Complicated relationships between declaration in Kotlin and usage in Swift Problems of iOS development KMM plugin for Android Studio
13. KMM plugin for AppCode 13
14. KMM plugin for AppCode Develop Kotlin Multiplatform projects in AppCode Highlighting, autocompletion for Kotlin Run | Debug iOS and Android apps 14 Go to declaration, refactorings and fi nd usages work for Kotlin, Obj-C and Swift
15. Demo 15 KMM plugin for AppCode
16. 🪄 16
17. What is a symbol Symbol • Name • Location • Attributes • Relationships with other symbols • … 17 Internal representation of the declaration of anything in the code. Symbol tables - the IDE's knowledge of classes, functions, variables, etc.
18. class Person { let name = "John" let surname = "Doe" let age = 42 // Very important function func greet() { print("Hi \(name)!") } } class Person let name: String let surname: String let age: Int func greet() -> Void Symbol table 18 What is a symbol
19. 19 https://vimeo.com/showcase/7769418/video/479319821 NSSpain 2020
20. Obj-C - Swift Cross Resolve Obj-C class AnotherObject: NSObject @interface AnotherObject : NSObject //... @end Naming Rules 20
21. Cross Resolve 21 Kotlin-Swift Cross Resolve
22. Symbols translation val helloString = "Hello from Kotlin!" var helloString: String { get } 22
23. MyShared.framework MyFramework.h MyFramework IDE How it works in Xcode val helloString = "Hello from Kotlin!" @property (readonly) NSString *helloString; objc var helloString: String { get } Kotlin compiler ⏳ Build project 23 Symbols translation
24. Kotlin compiler 24 Kotlin frontend Kotlin/Native backend Kotlin 
 Code IR MyShared.framework MyFramework.h MyFramework Symbols translation
25. Kotlin/Native backend 25 IR MyShared.framework MyFramework.h MyFramework Obj-C Symbol Structures Obj-C Symbols Swift Symbols Symbols translation
26. IDE How it works in KMM for AppCode val helloString = "Hello from Kotlin!" var helloString: String { get } Internal Compiler Structures @property (readonly) NSString *helloString; objc New 26 Symbols translation
27. Advantages of the new approach 🚀 Updates on the fl y 🎯 Go to Declaration, refactorings and etc. 😅 Tolerates mistakes 27 Symbols translation
28. Hooray! 
 Now you don't have to rebuild the framework after each Kotlin code change! 28 print(a.hello) SourceKit
29. Getting annotations from SourceKit What is SourceKit SourceKit request response Navigation Highlighting Autocompletion … 29
30. 30 SourceKit val helloString = "Hello!" import MyFramework Getting annotations from SourceKit Problem MyFramework ⁉ @property (readonly) NSString *helloString; MyFramework.h objc build
31. 31 SourceKit val helloString = "Hello!" print(a.helloString) Getting annotations from SourceKit Problem MyFramework @property (readonly) NSString *helloString; MyFramework.h objc val hello = "Hello!" print(a.hello) ⁉
32. 32 📁 MyFramework.framework/ 📁 Headers/ MyFramework.h 📁 Modules/ module.modulemap Info.plist MyFramework SourceKit Getting annotations from SourceKit Solution
33. 33 📁 MyFramework.framework/ 📁 Headers/ MyFramework.h 📁 Modules/ module.modulemap SourceKit After each Kotlin code change /iosApp/build/tmp/SourceKitFrameworkStubs/MyFramework.framework Getting annotations from SourceKit Solution
34. Optimizations 34 • Generate right before the opening of a Swift fi le • Ignore changes in comments and function bodies / / This is very important fun doImportantThings(): Int { val a = 1 val b = 2 return a + b } Getting annotations from SourceKit
35. 35 Getting annotations from SourceKit ✅
36. Project model 36
37. Project model 37
38. 38 Project model Gradle-only approach Kotlin shared Android app iOS app Gradle Gradle Xcode project Gradle Source of truth for iOS apple { iosApp { productName = "CocoaConferences" sceneDelegateClass = "SceneDelegate" launchStoryboard = "LaunchScreen" dependencies { implementation(project(":shared")) } } } iosApp/build.gradle.kts : ( )
39. 39 Project model Hybrid approach Kotlin shared Android app iOS app Gradle Gradle Xcode project kotlin { ios() cocoapods { summary = "Kotlin CocoaPods iOS Library" homepage = "https: / / jetbrains.com" podfile = project.file(" .. /xcode/Podfile") ios.deploymentTarget = "14.7" } } ioisMain/build.gradle.kts : + UNDER DEVELOPMENT
 COMING SOON
40. 40 Cross-resolve between Kotlin and Swift already exists, and you can try it right now in KMM plugin for AppCode Conclusions
41. Conclusions 41 In the future, Kotlin Multiplatform will become increasingly friendly to iOS developers
42. Conclusions 42 Moving KMM tooling forward is challenging, but func fun
43. Thank you! 43 What we talked about: • Kotlin Multiplatform intro • Current problems of the iOS world • KMM plugin for AppCode • How Kotlin-Swift cross-resolve works • Pleasing SourceKit • Project model • Conclusions @appcode @aydarmukh