nested-classes-multiplatform

A demo project that reproduces an issue where nested classes in Kotlin Multiplatform library cannot be used in Swift when accessed through another Kotlin Multiplatform library.

Project Overview

• common: Shared library (could be used for both a backend and mobile apps)
• mobile: Mobile library (could be used for shared view models/netowrking/etc). Uses common.
• An iOS app, located in apple/FooBar. Uses FooBarShared, which is generated from mobile.

Setup

1. Clone repo
2. Run ./gradlew :mobile:packForXcode to initialize the framework
3. Open apple/FooBar.xcodeproj and build the project

Important files

• apple/FooBar/AppDelegate.swift: example of a nested classes that cannot be used in Swift
• common/src/commonMain/kotlin/foo/bar/test/common/Fizz.kt: Kotlin classes in the common library
• mobile/src/commonMain/kotlin/foo/bar/test/mobile/Api.kt: Kotlin class that uses common classes and its own example classes
• mobile/build.gradle.kts: Grandle setup for mobile project

Notes

The following is taken from the header and cannot be used/accessed in Swift in any way:

__attribute__((objc_subclassing_restricted))
__attribute__((swift_name("CommonFizz.Hello")))
@interface FooSharedCommonFizzHello : FooSharedBase
- (instancetype)initWithMyName:(NSString *)myName __attribute__((swift_name("init(myName:)"))) __attribute__((objc_designated_initializer));
- (NSString *)component1 __attribute__((swift_name("component1()")));
- (FooSharedCommonFizzHello *)doCopyMyName:(NSString *)myName __attribute__((swift_name("doCopy(myName:)")));
- (BOOL)isEqual:(id _Nullable)other __attribute__((swift_name("isEqual(_:)")));
- (NSUInteger)hash __attribute__((swift_name("hash()")));
- (NSString *)description __attribute__((swift_name("description()")));
@property (readonly) NSString *myName __attribute__((swift_name("myName")));
@end;

In the generated header, a Imported declaration 'FooSharedCommonFizzHello' could not be mapped to 'CommonFizz.Hello' warning is generated on the swift_name attribute.

The following is the interface for the Api class that uses this type:

__attribute__((objc_subclassing_restricted))
__attribute__((swift_name("Api")))
@interface FooSharedApi : FooSharedBase
- (instancetype)init __attribute__((swift_name("init()"))) __attribute__((objc_designated_initializer));
+ (instancetype)new __attribute__((availability(swift, unavailable, message="use object initializers instead")));
- (void)argFromOtherModuleHey:(FooSharedCommonHey *)hey __attribute__((swift_name("argFromOtherModule(hey:)")));
- (void)nestedArgFromOtherModuleHello:(FooSharedCommonFizzHello *)hello __attribute__((swift_name("nestedArgFromOtherModule(hello:)")));
- (void)nestedArgFromThisModuleNest:(FooSharedNestNested *)nest __attribute__((swift_name("nestedArgFromThisModule(nest:)")));
- (void)noArgFunction __attribute__((swift_name("noArgFunction()")));
@end;

nestedArgFromOtherModuleHello is not visible in Swift, while the other functions work as expeted.