Support Route.inject() help in koin-ktor

[ValentinTrinque]

Note: I am a Kotlin beginner

I am currently working on integrating an HTTP API using ktor, using koin-ktor. While designing my endpoints routing, I wanted to inject the dependencies at the Route level instead of Application level. Indeed, I split my Routes in seperate files, one for each resource :

api/Application.kt

fun Application.endpoints() {
    routing {
        v1()
    }
}

fun Routing.v1() {
    route("/api/v1") {
        users()
    }
}

api/v1/Users.kt

fun Route.users() {
    val usersQueryRepository: UsersQueryRepository by inject()

    get("/users") {
        val users: List<UserDto> = usersQueryRepository.list()

        call.respond(users)
    }
}

Your library implements inject() (& co.) helpers at Application level only. I was thinking about making this available at Route level.

Here is a working implementation:

inline fun <reified T> Route.inject(name: String = "") =
        kotlin.lazy { (StandAloneContext.koinContext as KoinContext).get<T>(name, emptyParameters()) }

What do you think ? I would be glad to help!

[scottsteen]

What I would rather see is the functions defined in KoinComponent to not be associated with an interface. This would remove the need for the koin-ktor project. I plan to open another issue with this request though. Kotlin actually allows you to define functions that do not belong to a class!

To get around the limitation you face is to create a Kotlin object that implements the KoinComponent interface. This way I can call inject() anywhere I need to.

Example:

object KoinProxy : KoinComponent
...
val usersQueryRepository: UsersQueryRepository by KoinProxy.inject()
...

Something else to consider is to call startKoin() in the object's init block. E.g.

object KoinProxy : KoinComponent {
    init {
        startKoin(listOf(your_context))
    }
}

[arnaudgiuliani]

Hello @scottsteen

What I would rather see is the functions defined in KoinComponent to not be associated with an interface.

This is another issue. We'll continue here about ktor Route API integration.

[roelandmoors]

For me this is not usable because the inject happens at application start and not on a http request.
I would like to create a new service at every request to that route.
For now I do the inject in every get() method instead. Is there a better way?
Maybe this is more a Ktor problem then a Koin problem.

This is the extension method I use for now:

inline fun <reified T> PipelineContext<Unit, ApplicationCall>.inject(name: String = "") =
        kotlin.lazy { (StandAloneContext.koinContext as KoinContext).get<T>(name, emptyParameters()) }

[arnaudgiuliani]

@Baresse added the extensions for Route &
Routing. will be available in 1.0.0-beta-3.