Swift's flow.collect function only receives first value

Having created a simple flow in common code to emit incrementing values with a delay as follows:

flow {
    (1..10).forEach {
        emit(it.toString())
        delay(1000)
    }
}.flowOn(Dispatchers.Default)

When observing using Swift with:

class AModel: Kotlinx_coroutines_coreFlowCollector {    
    func emit(value: Any?, completionHandler: @escaping (KotlinUnit?, Error?) -> Void) {
        print("ios received " + (value as! String))
    }
}

val state: AModel = AModel()

flow.collect(collector: state) { (result: KotlinUnit?, error: Error?) in
    print("completion")
}

Actual: Only the first value is received and printed by the Kotlinx_coroutines_coreFlowCollector. Additionally the flows completion block is not executed. The same common code works on Android.

Expected: All values to be received and printed and the flow to complete once the last value has been received.

Kotlin: 1.4.10 Coroutines: 1.3.9-native-mt-2 Xcode: 12.0.1 iOS simulator: iPhone 11 running 14.0 Swift: 5

FYI @qwwdfsad this is the issue we discussed in the Kotlin 1.4 Online booth call.

[ciffa]

Could it be that you’re not calling the completion handler and therefore not clearing the queue?

func emit(value: Any?, completionHandler: @escaping (KotlinUnit?, Error?) -> Void) {
    print("ios received " + (value as! String))
    completionHandler(KotlinUnit(), nil)
}

[mattmook]

Yes @ciffa calling the completionHandler does make this work (tested with 1.4.3-native-mt)