Using flow as the return type of an API call-CodePudding

I am into kotlin and co-routines since last 8 months, as per my understanding it is not optimal usage of flow if we use it as the return type of an api call.

e.g:

fun getCoutries(): Flow<List<Country>> = flow {
   emit(apiInterface.getAllCountries())
}

I am seeing usage of flow like these in one shot api calls, I want to know if this should be discouraged or not. Since flow is to be a stream rather than being one shot.

CodePudding user response：

Flow is an asynchronous data stream that sequentially emits values and completes normally or with an exception. One shot api call is not a data stream so using Flow for that is an overhead. For a single api call I would use a suspend function with context switching to background thread:

fun suspend getCountries(): List<Country> = withContext(Dispatchers.IO) {
    apiInterface.getAllCountries()
}

Using a Flow depends on a particular use case. Anyway if you need a Flow you can always create it out of a suspend function:

fun getCountriesFlow(): Flow<List<Country>> = flow {
    // make request and emit items each ten seconds
    while(true) {
        emit(getCountries())
        delay(10000)
    }
}

So for a single api call it is better to use a suspend function. From the other hand Flow is a type that can emit multiple values sequentially, but it doesn't prevent the Flow from emitting only one value, so again it depends on the use case.