Hi, everyone! Recently, i started to develop web a...

# ktor

[Vasily Scherbakov]

Hi, everyone!
Recently, i started to develop web app using vaadin framework. My aim is to fetch data from REST API. I tried use ktor client for this, but i have the next problem:
i need to invoke suspend function in non suspend context(variable declaration). This is my view code:

class MainView : KComposite() {
    private val apiClient: ScenarioServiceClient = ScenarioServiceClientImpl("<http://localhost:5000>");
    private val root = ui {
        verticalLayout {
            horizontalLayout {
            div{
                addClassName("centered-content")
                 apiClient.getAvailableScenarios()
                    .forEach { scenario -> scenarioItemView(scenario) }
            }
        }
    }
}

This is how i use ktor:

class ScenarioServiceClientImpl(private val baseUrl: String) : ScenarioServiceClient {
    private val restClient: HttpClient = HttpClient(Apache)
    override suspend fun getAvailableScenarios() : List<ScenarioViewModel>{
        val scenarios = restClient.get<List<ScenarioViewModel>>("${baseUrl}/scenarios")}}

May be there is some way to invoke api call without suspend?

[Didier Villevalois]

Hi, I don't know Vaadin, so I'll give you some ingredients.
1. you need to have a coroutine scope bound to your MainView so that when it is destroyed the associated coroutine scope's job will be canceled (and with it, all the pending calls to your API)
2. then you can add a var availableScenarios: List<ScenarioViewModel>? = null
3. you can then add an init { launch { availableScenarios = apiClient.getAvailableScenarios() } } block
4. finally, in your div , you just have to test whether the availableScenarios is null or not, and display either a loading widget or the result.
All this will only work, if you can dynamically add children to your ui tree and that, somehow, KComposite rebuilds it view.
Hope this helps.

[Aleksei Tirman [JB]]

You can find this article helpful.

[Vasily Scherbakov]

thx guys!