Hey guys, I have a really random question about op...

# random

[omuomugin]

Hey guys, I have a really random question about operator for collections in Kotlin.
Is there something like if not empty let ? I’m always doing like below and I really wish to drop this local variable if possible.

val items = getItems()
if(items.isNotEmpty()) {
  doSomethingWith(items) // e.g map items etc..
}

[omuomugin]

I have a solution with using takeIf

getItems().takeIf { it.isNotEmpty() }?.let {
  doSomethingWith(it) // e.g map items etc..
}

but is there any better solution?

[karelpeeters]

Ideally this problem doesn't happen because doSomethingWith handles empty collections as well.

[omuomugin]

You’re right when doSomethingWith is the method for each items but when it comes to do something with list isNotEmpty is needed.

[karelpeeters]

Can you give an example? Now I'm curious.

[sitepodmatt]

agree with Karel, why can't doSomethingWith handle empty lists?

[omuomugin]

Well simple example is like you want to print items when there are items (don’t want to print if there were no items).

What happened the most recent was I had to build headers for request and this is done if only there were valid headers.

It might be rare but I think there are some use cases for handling theses empty or not.

[sitepodmatt]

okay so lets say do something is println, you dont want anything such as [] sent to screen when empty

[sitepodmatt]

I don't think you can get anything more succinct or clearer than takeIf { predicate }.also { } (also for side effects or let if assigning to something on the left)

[sitepodmatt]

you could make an extension on List but i cant see why you would

[rook]

Could also use firstOrNull() in this case. The name of the method doesn’t lend itself to readability for this case, but it does what you’re looking for.

[rook]

Just ignore the return value if it isn’t null

[omuomugin]

Through this conversation, I kind a agree with what Matt said

I don’t think you can get anything more succinct or clearer than takeIf { predicate }.also { } (also for side effects or let if assigning to something on the left)

Anyway thanks for having discussion for this random question