Avoid ANRs when collecting flows in Presenters

[cwsiteplan]

Hi,

I just ran into the issue that the Presenter was collecting flows from a repository on the default (main) dispatcher -> producing ANRs.

so we just have to be careful when using .collectAsState() and for usages with flows that should be collected in the background we can specify .collectAsState(initialValue, Dispatchers.IO)

i wonder if someone has any lint rules or sth in place to not fall into the trap.

[JakeWharton]

It sounds like your Flow should have used flowOn(IO) before it ever got near your UI. Just like how suspending functions should be "main" safe, Flows should be the same. It's perfectly acceptable to encapsulate blocking work within one, but that Flow should force itself to an appropriate dispatcher before it leaks out to somewhere where that context can be lost.

[cwsiteplan]

oh sorry, wasn't aware of that! (using withContext() for suspend fun was clear - just didn't know about the equivalent for flows).

Thanks for the input!