is there a clever way to inject my dependencies when using extension functions of Route? atm i have a method like this but i always have to pass through my dependencies to other method calls. this feels a bit clumsy

I'm curious about this as well. I have quite a few routes in my API and some of them have more than 6 dependencies. This is troublesome specially in cases where routes are nested (e.g.

/accounts/123/items/123

) - then you have to nest these functions and it becomes a dependency hell. I'm thinking about refactoring my app, this is the approach I currently have though of:

interface AccountService {
    suspend fun getAccounts(): List<Account>
}

abstract class Handler(private val path: String) {
    fun init(root: Route) {
        root.route(path) {
            routes()
        }
    }

    protected abstract fun Route.routes()
}

class AccountHandler(
    private val accountService: AccountService
) : Handler("/accounts") {

    override fun Route.routes() {
        get {
            call.respond(accountService.getAccounts())
        }
        
        // List other API calls here.
    }
}

fun Application.main() {
    val accountService = object : AccountService {
        override suspend fun getAccounts() = emptyList<Account>()
    }

    // List all handlers here (order is important).
    val handlers = listOf<Handler>(
        AccountHandler(accountService)
    )

    routing {
        route("/api") {
            handlers.forEach { handler ->
                handler.init(this)
            }
        }
    }
}

Haven't yet implemented this in prod, but maybe it will work out for you.

what i do now is that i have all my code extracted to handlers and in the route itself i only extract the json from the request and the handler returns the response json which i return in the route function with call.respond(someJsonObject). i am not sure if i want to pass the call object to the handler .. for now i decided against it. problem with that approach is the i have some validation in route and some of it in the handler.

You are right, the

ApplicationCall

object should not be passed to your

*Handler

classes. The API/Json stuff should remain on extension functions and business logic should stay on services (or handlers as in your case).

i know that ktor tries to be unbiased .. but i wonder if there is something like a best practice approach to that problem.

Both the Kodein and Koin dependency injection frameworks have Ktor features that you can install to retrieve services on your routes

If you think you have too many dependencies, the answer is not to introduce a magical DI system, but to refactor and extract a higher level abstraction that may be missing.

DI framework would be the last step for me .. i have no need for that atm. the question was more about the extension functions in combination with dependencies. i can pass them to the Route.someFunc(dep1, dep2) but i can't store them in a field so they are reachable from other functions. (btw using the locations API)