I'm pulling my hair out trying to use "async" datastore stuff. When I access my "special" once-n-onl...

# getting-started

[Travis Griggs]

I'm pulling my hair out trying to use "async" datastore stuff. When I access my "special" once-n-only-one preferencesDataStore .data, I get a flow on the data. But what if no preferences have been saved? I want to initialize a startup variable based on its contents. But if non has been saved yet, it just blocks forever. I've tried various incantations of map/latest with or without the orNull adds. Is there no way to get "the current value or something else if there is not yet any value"?

[Youssef Shoaib [MOD]]

I think what you need is stateIn

[Travis Griggs]

firstOrNull() worked as well. I don't get why lastOrNull would block indefinitely, but firstOrNull() happily returns null right away

[Youssef Shoaib [MOD]]

to find out the last thing, you need to collect everything first. It is strange that firstOrNull works though

[Youssef Shoaib [MOD]]

Careful btw because firstOrNull is a terminal operator

[Travis Griggs]

what do you mean that it's a terminal operator? I find that I can then update the pref's value to have a value, and use the same flow object (not create a new one) and ask it firstOrNull() and it now returns the newly updated value.

[Youssef Shoaib [MOD]]

That kind of makes sense, I guess. That's likely because the flow given to you by the library is a shared one, and hence the terminal operator doesn't actually result in termination.

[Travis Griggs]

I can't say I love "flow" programming. But I hope I'll get it. Maybe then I'll be awed by it

[Daniel Pitts]

It's possible you're using flow in a way it's not actually intended. It sounds like this particular case you want to use MutableStateFlow.

[Travis Griggs]

The PreferencesDataStore defines the type of Flow I get , i think?

[Daniel Pitts]

I see. I’m not familiar with that api.