I thought I understood kotlin coroutines :man-facepalming:

# coroutines

[Tower Guidev2]

I thought I understood kotlin coroutines 🤦‍♂️

[Tower Guidev2]

I have this function in my repository of my android application

override suspend fun displayItem(contentId: Long): DisplayItemState =
        withContext(<http://Dispatchers.IO|Dispatchers.IO>) {
            val encodedUrl = encode("${BuildConfig.MY_CONTENT_C_URL}$contentId", StandardCharsets.UTF_8.name())
            DisplayItemState(Intent(Intent.ACTION_VIEW, Uri.parse("${BuildConfig.MY_MOBILE_CLICK}${loginToken()!!}?url=$encodedUrl")))
        }

[Tower Guidev2]

which is called in this init{} of my viewModel


private lateinit var notificationDisplayItem: DisplayItemState

init {
if (isNotification) viewModelScope.launch {
when (notificationAction) {
VALUE_ARG_SPECIALTY_NOTIFICATION_ACTION_VIEW -> notificationDisplayItem = repository.displayItem(contentId!!)
VALUE_ARG_SPECIALTY_NOTIFICATION_ACTION_SAVE -> TODO("Should never occur as save broadcast receiver")
VALUE_ARG_SPECIALTY_NOTIFICATION_ACTION_DISCARD -> TODO("Should never occur as discard broadcast receiver")
else -> TODO("Unexpected notification action $notificationAction")
}
}
}

[Tower Guidev2]

the issue is the lateinit variable notificationDisplayItem is not being initialized
how can i get my code to "wait" for the call to repository.displayItem(contentId!!) to respond

[Sam]

If I’m understanding right, you want the constructor to suspend? That’s not possible, especially since this constructor will presumably be invoked by the platform

[Sam]

Why does displayItem need to suspend, though?

[Tower Guidev2]

oh , thats a good question 🤔

[Peter Farlow]

does the function loginToken() also suspend? If so, displayItem needs to suspend

[Sam]

Didn’t spot that, it’s very well hidden 😄

[Tower Guidev2]

does the function loginToken() also suspend? If so, displayItem needs to suspend

yes it does

[Tower Guidev2]

how i got to this "position" is that android studio flags the encode call with "P_*ossibly blocking call in non-blocking context could lead to thread starvation*_"

[Tower Guidev2]

and i was investigating how i could resolve this
i have a feeling encode is not that big an issue

[Sam]

Where is that encode function coming from? There are a few things that could cause that warning, e.g. declaring certain types of exception

[Tower Guidev2]

import java.net.URLEncoder.encode

[Sam]

Hah 😄 so it looks like the warning is because that method declares UnsupportedEncodingException, which extends IOException. The IDE sees that and assumes that IOException = IO = blocking, which is a pretty big leap 😄

[Sam]

Your feeling is correct, you can safely suppress that warning

[Tower Guidev2]

Screenshot 2023-03-09 at 17.08.59.png

[Tower Guidev2]

thanks for your time
😄

[Robert Williams]

Just to answer the original question, in the more general case where you do actually need to do something suspending on init and potentially wait for it later you can use a Deferred:

private val notificationDisplayItem: Deferred<DisplayItemState> = viewModelScope.async {//suspending work}

where it's needed:

notificationDisplayItem.await() //returns result, suspends or throws