Error: Suspension functions can be called only within coroutine body for the code doing a remove and...

# kotlin-native

[Daniel]

Error: Suspension functions can be called only within coroutine body for the code doing a remove and after a logout:

suspend fun doLogout(token: String) {
    val userId = appService.currentUser?.id

        realm.write {

            var user = query<UserInfo>("_id = $0", userId).first().find()
            if (user != null) {
                val productIndex =
                    user.FCMToken.withIndex().findLast { it.value == token }!!.index

                user = findLatest(user)!!.also {
                    it.FCMToken.removeAt(productIndex)
                }
                copyToRealm(user)

                appService.currentUser?.logOut() // Suspension functions can be called only within coroutine body

            }
        }
}

Is there anyway to fix this without changing much code?
I need to do first the db operation then logOut()

[Mitchell Syer]

suspend fun doLogout(token: String) {
    val userId = appService.currentUser?.id

        realm.write {

            var user = query<UserInfo>("_id = $0", userId).first().find()
            if (user != null) {
                val productIndex =
                    user.FCMToken.withIndex().findLast { it.value == token }!!.index

                user = findLatest(user)!!.also {
                    it.FCMToken.removeAt(productIndex)
                }
                copyToRealm(user)
            }
        }
    appService.currentUser?.logOut()
}

This should work as long as realm.write is not launching the code in another thread

[Daniel]

It is

[Daniel]

sometimes the logout happens first..

[Daniel]

How can I avoid this?

[Mitchell Syer]

This might work then

suspend fun doLogout(token: String) {
    val userId = appService.currentUser?.id
    coroutineScope {
        realm.write {

            var user = query<UserInfo>("_id = $0", userId).first().find()
            if (user != null) {
                val productIndex =
                    user.FCMToken.withIndex().findLast { it.value == token }!!.index

                user = findLatest(user)!!.also {
                    it.FCMToken.removeAt(productIndex)
                }
                copyToRealm(user)

                launch { appService.currentUser?.logOut() }
            }
        }
    }
}

[Mitchell Syer]

Or not, I forgot that coroutineScope wouldnt work well with realm.write if it launches another thread

[Daniel]

Any solution?

[Mitchell Syer]

Found a solution

suspend fun doLogout(token: String) {
    val userId = appService.currentUser?.id
    val deferred = CompletableDeferred<Unit>()
        realm.write {

            var user = query<UserInfo>("_id = $0", userId).first().find()
            if (user != null) {
                val productIndex =
                    user.FCMToken.withIndex().findLast { it.value == token }!!.index

                user = findLatest(user)!!.also {
                    it.FCMToken.removeAt(productIndex)
                }
                copyToRealm(user)
            }
            deferred.complete(Unit)
        }
    deferred.await()
    appService.currentUser?.logOut()
}

[Daniel]

Could you please explain a bit the logic?

[Mitchell Syer]

CompleteableDeferred is an implementation of Deferred from async/await in Kotlin that has public methods to complete the Deferred. Calling Deferred.await() waits until the Deferred is complete and then allows execution to continue. And calling Deferred.complete with a value sets Deferred as complete, allowing execution to continue

[mkrussel]

I'm assuming that ream.write is a blocking call, in which case it should be run in a new coroutine (suspend functions should be main thread safe).

So you would wrap the call to realm.write in a withContext(<http://Dispatchers.IO|Dispatchers.IO> { } And then make the call to logOut after the withContext returns. This is similar to the CompletableDeferred solution above, but I think more idiomatic.

[mkrussel]

If realm.write is launching it's own thread, then I would probably use the suspendCoroutine function or suspendCancellableCoroutine if realm gives you a way to cancel.

[Daniel]

@Mitchell Syer Unfortunately logOut method still happens before the realm.write

[Mitchell Syer]

Thats very unlikely unless something else is wrong. The code is setup to wait until realm.write's execution is finished. Maybe check/log if user is null or other similar issues

[mkrussel]

realm.write is already suspending, so neither of our suggestions are needed