Is there any more Kotlin esque way to achieve the effect out

Question

Is there any more Kotlin esque way to achieve the effect outlined here

gregorbg · Answer

Background The class JavaObject has two properties Foo and Bar which may be null I want to map them to instances of a Kotlin class but only for those instances where both fields are not null

gregorbg · Answer

Migrating the `JavaObject` class in the first place is not an option

wbertan · Answer

Maybe like this ``` javaObjects mapNotNull val foo = it fooProperty return mapNotNull null val bar = it barProperty return mapNotNull null KotlinDataClass foo bar ```

wbertan · Answer

At least is more readable I guess

gregorbg · Answer

Thanks for the suggestion I for one would argue that the long `return mapNotNull null` kills readability even more but I guess that s just personal taste

wbertan · Answer

I agree I don t like even the early `return` in the code but I remember having this case before and the team agreed was more readable those `return ` than the enclosed `let`s

wbertan · Answer

thinking face Can create an extension too ``` fun lt T Z gt Pair lt T Z gt pairOrNull Pair lt T Z gt val first = first return null val second = second return null return Pair first second fun doSomething javaObjects List lt JavaObject gt List lt KotlinDataClass gt = javaObjects mapNotNull Pair it fooProperty it barProperty pairOrNull let foo bar gt KotlinDataClass foo bar ```

Ruckus · Answer

Honestly I d avoid the functional approach in this case ``` fun doSomething javaObjects List lt JavaObject gt List lt KotlinDataClass gt val data = mutableListOf lt KotlinDataClass gt for j in javaObjects data += KotlinDataClass j fooProperty continue j barProperty continue return data ```

Alowaniak · Answer

Or make a `NullableKotlinDataClass` factory method ``` fun NullableKotlinDataClass foo Any bar Any KotlinDataClass return KotlinDataClass foo return null bar return null fun doSomething javaObjects List lt JavaObject gt List lt KotlinDataClass gt return javaObjects mapNotNull NullableKotlinDataClass it fooProperty it barProperty ``` Perhaps as an extension function on `JavaObject` so you can do ```fun JavaObject toKotlinDataClassOrNull KotlinDataClass return KotlinDataClass fooProperty return null barProperty return null fun doSomething javaObjects List lt JavaObject gt List lt KotlinDataClass gt return javaObjects mapNotNull JavaObject toKotlinDataClassOrNull ```

uhe · Answer

For completeness sake you can also just use an `if` instead of the `let` nesting ``` class Foo val a String val b String class Bar val a String val b String fun foo foos List lt Foo gt List lt Bar gt = foos mapNotNull if it a = null amp amp it b = null Bar it a it b else null ```