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Title
# flow
a

Alex

08/31/2021, 10:39 AM
Why can't we 
.map
a 
StateFlow
and have it still be a 
StateFlow
? Why the conversion to a regular 
Flow
?
c

CLOVIS

08/31/2021, 10:49 AM
Because 
.map
can suspend, the child flow needs its own scope. You can convert a flow into a StateFlow with 
.stateIn
.
🙏 2
c

Chris Fillmore

09/01/2021, 1:00 AM
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:
Copy code
val numberFlow = MutableStateFlow<Int>(0)

val lessThanZero = numberFlow.filter { it < 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?
🙏 1
a

Alex

09/01/2021, 8:11 AM
@Chris Fillmore 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.
👍 1
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