while using flow.first() operator, it throws exception when flow is empty as docs say, but I am fetc...

# coroutines

[Vivek Sharma]

while using flow.first() operator, it throws exception when flow is empty as docs say, but I am fetching list from database using a flow and checking if that flow.first() , and if the list is empty , does it mean flow is empty ?

[wasyl]

What are you asking specifically? first() does exactly what it says, returns the first element, or throws if the flow completes before emitting anything

[wasyl]

If you have a Flow<List<T>> then first() will still do the same thing, if nothing is emitted and the flow completes then first() will throw an exception. If the flow emits a value, it will return that value

[wasyl]

If that value is an empty list, you’ll get an empty list

[Vivek Sharma]

I am asking that if I get empty list emitted from flow, will first() throw exception ?

[Vivek Sharma]

when flow will be empty or say will not emit anything?

[wasyl]

It will not throw an exception because the flow is not empty, an empty list is a value

[wasyl]

It’s easy to check yourself

val result = flowOf(emptyList<String>())
    .first()
println(result)

[gildor]

Usually Flow from database never complete, it just emit current state of your request, so first() will suspend until it receive first result and after that return it

[Vivek Sharma]

okay I got it thanks @Luka @gildor