Question about use of lateinit var I ve only seen it used in

Question

Question about use of lateinit var I ve only seen it used in class variables but I recently came across it in a PR from someone new to Kotlin that used it inside a method call What are the patterns and advice for using lateinit var inside methods Or should it be avoided Is the below use of lateinit valid ``` fun degreesToDirection degrees Float Direction var smallestDistance Float = Float POSITIVE INFINITY lateinit var direction Direction degreesMapping entries forEach if abs it value degrees 0f lt smallestDistance direction = it key smallestDistance = degrees 0f it value return direction ```

Joffrey · Answer

There is nothing really wrong about this `lateinit var` per se But doing this sort of loop to initialize a variable in Kotlin is usually a smell For instance is it expected to iterate over all the mappings here Usually the first match should stop the loop

Javier · Answer

I can t think a lot about it now but you probably can change that to reduce + first or fold + first and so on so you can avoid mutability But not sure if the alternative is so readable compared to the current one

Vampire · Answer

```fun degreesToDirection degrees Float = degreesMapping minByOrNull mappedDegrees gt abs mappedDegrees degrees 0f key```

Vampire · Answer

gt For instance is it expected to iterate over all the mappings here Usually the first match should stop the loop First match when searching for a minimum wink

Vampire · Answer

As far as I understood lateinit is practially always a smell be it as property or not and is mainly for integrate into existing frameworks like Spring that sets the value after creating the object and similar

Joffrey · Answer

Lol indeed for a minimum you have to I actually didn t really read the code in details I m on mobile but the general pattern of declaring a var and init via a loop seemed wrong

Starr · Answer

isn t there `minBy` `maxBy` for this kind of stuff

Vampire · Answer

Yes I just gave the imho proper code just see my first comment

Joffrey · Answer

In Kotlin 1 7 you shouldn t need `minByOrNull` + ` `

Vampire · Answer

Which else would I use I only found `minBy` which is deprecated and should be replaced by `minByOrNull`

Javier · Answer

they removed minBy in 1 6 to bring back it in 1 7

Javier · Answer

the previous implementation of minBy can be nullable so to follow the standard naming they removed for one version so they can have both minBy and OrNull in 1 7

Vampire · Answer

I see o O

Vampire · Answer

Or ```fun degreesToDirection degrees Float = degreesMapping minWith compareBy mappedDegrees gt abs mappedDegrees degrees 0f key```

Vampire · Answer

Hm <https kotlinlang org api latest jvm stdlib kotlin collections map > does not display `minBy`

Vampire · Answer

And <https kotlinlang org api latest jvm stdlib kotlin collections min by html> shows `minBy` only not deprecated for common js and native but deprecated for jvm

Joffrey · Answer

Strange they re supposed to be back <https kotlinlang org docs whatsnew17 html min and max collection functions return as non nullable>

Vampire · Answer

Maybe a documentation problem due to the back and forth with deprecation

Rachel Carandang · Answer

Wow thanks for the good discussion Good to know