A modern programming language that makes developers happier.

kotlinlang

Why can't we `.map` a `StateFlow` and have it still be a `StateFlow`? Why the conversion to a regular `Flow`?

Because `.map` can suspend, the child flow needs its own scope. You can convert a flow into a StateFlow with `.stateIn`.

I asked the same question a month ago, but once I thought about it I realized it didn’t make sense to map a StateFlow to another StateFlow:
<https://kotlinlang.slack.com/archives/CRJCTR5PD/p1626814749057400>

For example, consider the following code:
```val numberFlow = MutableStateFlow&lt;Int&gt;(0)

val lessThanZero = numberFlow.filter { it &lt; 0 }

// Suppose for a moment that filter/map could return a StateFlow, how would the below work:
val currentValue = lessThanZero.value

// What's the value of currentValue?```

<@U019NA2NYTX> yeah, for `.filter` this is easy, but for `map` its harder to see, since map will always return a value. `map` being able to suspend solves the question because then it might suspend for a while (on first submision) in which no value is present in the resulting stateflow, which is not allowed.