Given a `val isLoggedIn: Flow<Boolean>` that can emit `true` or `false` in any order and multi...

# coroutines

[zak.taccardi]

Given a val isLoggedIn: Flow<Boolean> that can emit true or false in any order and multiple times each - what would be the best way to observe when it switches from true to false ? I would like to run a function when the user logs out - meaning the Flow<Boolean> emits true then false?

val isLoggedIn: Flow<Boolean>

isLoggedIn
  // <-- what operators do I need here?
  .onEach { 
    onLogout()
  }
  .launchIn(scope)

[Tim Malseed]

Could you use distinct, and then just check if your value is false in you onEach block?

[Zach Klippenstein (he/him) [MOD]]

.distinctUntilChanged()
.filter { it }

[zak.taccardi]

oh that was easy

[zak.taccardi]

lol

[zak.taccardi]

wait I think I want the inverse

[Tim Malseed]

Yeah, filterNot { it }

[zak.taccardi]

but if the first value is false - won’t it emit and incorrectly call onLogout()

[zak.taccardi]

I specifically want to run a function only when the stream switches from true to false

[zak.taccardi]

so a single flow { emit(false) } should not trigger the onLogout()

[Tim Malseed]

I'm not sure what this would look like. Some kind of buffer? Maybe have a look at what distinct does under the hood?

[zak.taccardi]

I think the following may work

[zak.taccardi]

.distinctUntilChanged()
.drop(1)
.filterNot { it }

[zak.taccardi]

so false would not pass through the filter, but false, true, false would and true, false would as well

[Tim Malseed]

Hah that was also easy

[satyan]

You could also use the areEquivalent(old,new) parameter of distinctUntilChanged to only match old = true and new = false