Getting the KMP viewmodel from swift with koin (cleanest way I guess)

[frankois944]

Hi every one,
I found a way to get the KMP viewmodel from a ios/swift project like on Android

• make the koin scope available from swift

Store the koin scope in your swift (or kotlin) code

        let koinApplication = AppInitKt.startApp(...)        
        AppContext.shared.koinApplication = koinApplication

• make available the kotlin method getOriginalKotlinClass available from swift

On iOSMain target :

public fun getOriginalKotlinClass(objCClass: ObjCClass): KClass<*>? = getOriginalKotlinClass(objCClass)`

• create some helper to complete the jobs.

private class KoinQualifier: Koin_coreQualifier {
    init(value: String) {
        self.value = value
    }
    var value: String
}

extension ViewModel {
    static func getInstance<T: ViewModel>(qualifier: String? = nil, parameters: [Any]? = nil) -> T {
        if let ktClass = Shared.getOriginalKotlinClass(objCClass: Self.self) {
            var koinQualifier: Koin_coreQualifier?
            if let qualifier = qualifier {
                koinQualifier = KoinQualifier(value: qualifier)
            }
            
            if let instance = AppContext.shared.koinApplication?.koin.get(clazz: ktClass,
                                                                          qualifier: koinQualifier,
                                                                          parameters: {
                .init(_values: .init(array: parameters ?? []), useIndexedValues: true)
            }) {
                return instance as! T
            }
        }
        fatalError("Cant resolve ViewModel \(self)")
    }
}

• get the kmp viewmodel from swift

MyKMPViewModel.getInstance(parameters: ["IOS-MyFirstScreenWithMacro"])

full exemple at my playground https://github.com/frankois944/kmp-mvvm-exploration

[osrl]

here is how I use koin from swift side:

Koin.swift

typealias KoinApplication = Koin_coreKoinApplication
typealias Koin = Koin_coreKoin


extension KoinApplication {
    static let shared = KoinIOSKt.doInitKoinIos(doOnStartup: {
        print("Koin started")
    }, appDeclaration: { app in
        app.properties(values: ["BASE_URL": try! Configuration.value(for: .baseUrl) as String])
    })

  @discardableResult
  static func start() -> KoinApplication {
    shared
  }
}

func inject<T : AnyObject>() -> T {
    return KoinApplication.shared.koin.get(objCClass: T.self) as! T
}

func inject<T : AnyObject>(param: Any?) -> T {
    return KoinApplication.shared.koin.get(objCClass: T.self, parameter: param) as! T
}

KoinIOS.kt (iOS Main target)

@Suppress("unused")
fun initKoinIos(
    doOnStartup: () -> Unit,
    appDeclaration: KoinAppDeclaration
): KoinApplication {
    val koin = initKoin {
        module {
            single { doOnStartup }
        }
        appDeclaration()
    }

    setCrashlyticsUnhandledExceptionHook()

    return koin
}

//this currently only excepts single parameter but it can be improved
fun Koin.get(objCClass: ObjCClass, parameter: Any?): Any {
    val kClazz = getOriginalKotlinClass(objCClass)!!
    return get(kClazz) { parametersOf(parameter) }
}

fun Koin.get(objCClass: ObjCClass): Any {
    val kClazz = getOriginalKotlinClass(objCClass)!!
    return get(kClazz)
}

fun Koin.get(objCProtocol: ObjCProtocol): Any {
    val kClazz = getOriginalKotlinClass(objCProtocol)!!
    return get(kClazz)
}

ContentView.swift

//ObservedViewModel is from KMP-ObservableViewModel library
@ObservedViewModel private var myViewModel: MyViewModel = inject()

This can even be improved with a property wrapper

@propertyWrapper
struct Inject<T : AnyObject> {
    lazy var wrappedValue: T = { inject() }()

    init() { }
}

@Inject private var myViewModel: MyViewModel

I couldn't find a way to use the property wrapper with @ObservedViewModel though. So I'm using normal property initializer with inject()

[frankois944]

Thanks for your approach, I see you're using the rickclephas library for the viewmodel, not the official one.
Anyway, just be sure the init() and onCleared() callback are correctly called when it's necessary.

[osrl]

this is not specific to the viewmodels. any class can be injected with this.

[frankois944]

Yes I understand, I was stuck on viewmodel injection.

[osrl]

this should be working with the normal viewmodels too.