Hi! I want to do something if a

java.io.File

variable is null or not readable. In Java this vould be

if (myFile == null || !myFile.canRead()) {
    // error!
}

which works always because of short-circuit evaluation. IntelliJ translates the above code to:

if (simDesc == null || !simDesc!!.canRead()) {
    // error!
}

which is a bit ugly IMHO. Any idea on making it more idiomatic?

thecipster: it seems

simDesc

is not a local variable but a mutable property. either save the value to a local variable, make the property immutable (

val

) or use some tricks like

simDesc.takeIf { it.canRead() }?.let { /* do stuff */ }

I kinda feel like the current state of dealing with

Boolean

returning methods/properties on nullable objects is not very satisfying

@kirillrakhman, @uhe thanks for the reply. Unfortunately

simDesc

must be a mutable property (

var simDesc: File? = null

) because Java library. The trick with

takeIf

is nice but hardly more readable 🙂. I think that in this case the compiler knows enough to avoid the

!!

operator.

you can't avoid it. it's perfectly possible that

simDesc

is null on the second branch

it could be set to null on a different thread

OK now i see it, i wasn't considering multithreading issues

also you can do

if (simDesc?.canRead() != true)

but that won't help you, if you need to access the value again

I just tried with copying to a local variable and indeed the compiler is smart enough to consider short-circuit evaluation and removes the

!!

. Thanks a lot! 👍

you can read up on smart casts here: https://kotlinlang.org/docs/reference/typecasts.html