Is there a more kotlinish version for this? ```val...

# getting-started

[Pihentagy]

Is there a more kotlinish version for this?

val list: List<Int> = someCalculation()
if(list.isNotEmpty()) { doSomethingWith(list) }

The only downside of the above is that you have to declare a list variable. (I like how you can use apply and avoid creating local variables
)

[Sam]

someCalculation().takeIf { it.isNotEmpty() }.let { doSomethingWith(it) }

[Riccardo Lippolis]

@Sam it should be ?.let { ... } if doSomethingWith should only be executed when the list is not empty

[Vampire]

You miss a ? otherwise you call the method with null if the list is empty

[Sam]

Ohhh, gotcha 👍 thanks!

[Sam]

someCalculation().takeIf { it.isNotEmpty() }?.let { doSomethingWith(it) }

[Pihentagy]

Ohh, thanks. works, but I guess it is worth to write some custom extension function then to make it clearer.

someCalculation().runIfNonEmpty { doSomethingWith(this) }

[Youssef Shoaib [MOD]]

someCalculation().ifNotEmpty { doSomethingWith(it) }

Edit: seems like I had a false memory that this exists lol

[Sam]

👍 I've seen some YouTrack tickets for ifNotEmpty and also for a more generic runIf function. Seems like there's a gap here.

[Riccardo Lippolis]

ifNotEmpty might be confusing seeing as there is already an ifEmpty extension function on Collection that returns a default value if the list is empty

[Sam]

Well, ifNotEmpty could return a value too, even if it doesn't end up being used in all scenarios

[Riccardo Lippolis]

that's true of course, if the intent of the functions is clear and consistent across ifEmpty and ifNotEmpty , I am in favour 🙂

[Marian Schubert]

off-topic: in this case I would put ifEmpty check inside doSomethingWith (e.g. if empty then return - guard clause) or make it work gracefully with empty collection.

[Pihentagy]

True, but actually doSomething is a sendNotification(SomeDto(it.map{ e -> e.id })) , where sendNotifiation can handle many types of notifications, and SomeDto is just a DTO class.

[okarm]

I argue that your original code is already the most Kotlin Kotlin, unless this example of yours is somewhere in the middle of a chain.

A simple if expression is the cleanest, most understandable, most concise and most straightforward version of this kind of code that you can write. No need for the ballast of higher order wrappers just for conditional execution.

[Pihentagy]

Maybe, but then what about let? This case is just the generalization of let.

val x = maybeNull?.let { process(this) }

vs

val y = maybeEmpty.letNotEmpty { process(this) }

[Pihentagy]

No separate type for nonempty collection though...

[Vampire]

He meant 'use neither "let" nor "letNotEmpty" but keep the "if" you showed in your original post'.

[Vampire]

More a matter of taste I'd say, though. 🙂

[okarm]

☝️ That is for sure, and my bike's shed will be a nice dark green, thank you very much.