Android Coroutine function callback

user_5496625 0
Viewed 1692

Here is my fun in the Repository that returns me the String Id from the Group name

@Suppress(“RedundantSuspendModifier”)
@WorkerThread
suspend fun fetchGroupId(groupName: String): String {
      return groupDao.fetchGroupId(groupName)
}

And this is the function on the ViewModel

fun getGroupId(groupName: String) = scope.launch(Dispatchers.IO) {
      groupId = repository.fetchGroupId(groupName)
}

Now I want this group Id on the Activity side what I need to do?

kotlinx.coroutines kotlin android
3 Answers

You can use callback by using Higher order function as callback parameter to provide data back to calling method like below :

fun getGroupId(groupName: String, callback: (Int?) -> Unit) = scope.launch(Dispatchers.IO) {
    callback(repository.fetchGroupId(groupName))
}

This method would be used like below in your Activity:

mViewModel.getGroupId("your group name here") { id ->
    // Here will be callback as group id
}
user_102713340

You can use an interface something like :-

interface GroupIdViewContract{ fun returnId(groupId : String) }

in ViewModel

fun getGroupId(groupName: String) = scope.launch(Dispatchers.IO) {
groupId = repository.fetchGroupId(groupName)
viewContract?.returnId(groupId)
}

then you can implement this interface in your activity and you can easily get this group id in your activity

user_77934780

That's what you need Callbacks and Kotlin Flows. For example Single-shot callback:

interface Operation<T> {
    fun performAsync(callback: (T?, Throwable?) -> Unit)
}


suspend fun <T> Operation<T>.perform(): T =
suspendCoroutine { continuation ->
    performAsync { value, exception ->
        when {
            exception != null -> // operation had failed
                continuation.resumeWithException(exception)
            else -> // succeeded, there is a value
                continuation.resume(value as T)
        }
    }
}
user_3458100
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