Hello everyone, I have a question about extracting...

# ktor

[Rui]

Hello everyone, I have a question about extracting routes. So I extracted them and put them in separate files, but the question is, if these different routing all need to hold the references to same objects, where to put those objects?
More specifically, I have two routing files called Order.kt and Item.kt, and both of them need to use an instance of ItemService class. Then where should I put this

lateinit var itemService: ItemService

For now this is what I do, in Order.kt file:

lateinit var itemService: ItemService
fun Route.order() {
  post<Order> {
    init(...)
  }

  get<Order> {
    init(...)
  }
}

init(...) {
  itemService = ItemService(...)
}

and in Item.kt file

fun Route.item() {
  post<Item> {
    init(...)
  }
  get<Item> {
    init(...)
  }
}

Basically I put those common objects and their initialization method in one of the routing files, and other routing file can have direct access to those objects and methods.
I wonder what is the more proper way of organizing this? Appreciate any kinds of input !

[Marc Knaup]

You could simply pass whatever dependencies Route.order() needs to the function as parameters.

Alternatively you could use a dependency injection framework (and pass that as a function parameter).

You could also write a feature that puts references into the call and makes them available as an extension property to the call.

[Rui]

@Marc Knaup those objects in need will only be initialized when one of the routing gets called, with values from http parameters.
Please note the init(...) method.
In that case, what's the best practice?

[Marc Knaup]

Hmm I think I don’t fully understand your issue.
Why don’t you call init() in post<Order> { … } for example and return the ImageService (and others)?

[Marc Knaup]

both of them need to use an instance of ItemService class

and

those objects in need will only be initialized when one of the routing gets called, with values from http parameters

are conflicting. Should they share an instance of not?
If they should share one, then the instance shouldn’t depend on request parameters 🤔

[Rui]

@Marc Knaup or to put it this way, all the routing needs to use ItemService, but they need to create their own ItemService object based on parameter values in the http request.
Please see how I put itemService as a lateinit var, and each routes will initialize it with values from http request when getting called, that's why I call init(...) in all the routes

[Marc Knaup]

Yeah it will definitely not work that way. All routes will overwrite each other’s itemService

[Marc Knaup]

That’s why I’m asking about a simple

val imageService = init(…)

[Marc Knaup]

In the routes

[Rui]

@Marc Knaup yes in my example itemService gets overridden by each other, but somehow it works fine.
I can change it to

val imageService = init(…)

then where should I put the definition of init(...) method?

[Marc Knaup]

That’s the thing with race conditions. They may or may not cause mayhem 😄 It will likely cause issues randomly.

The definition of init you can have wherever you want.
if it just initializes an ImageService it should be somewhere nearby.

It’s difficult to say without knowing more.

[Rui]

@Marc Knaup thanks for answering!