Use of Boolean? in if expression
If I have a nullable Boolean b
, I can do the following comparison in Java:
Boolean b = ...;
if (b != null && b) {
/* Do something */
} else {
/* Do something else */
}
In Kotlin, I can achieve the same by using the !!
operator:
val b: Boolean? = ...
if (b != null && b!!) {
/* Do something */
} else {
/* Do something else */
}
However, the use of !!
feels a bit sketchy to me, circumventing the null safety system.
Is there a more elegant approach for this?
Edit It seems I oversimplicated a bit. For local variables, as Banthar shows, it does work. However, my Boolean b
is actually a "property with a backing field" (I'm not really up to speed yet what this imposes). This is the result:
You can compare nullable boolean with true
, false
or null
using equality operator:
var b: Boolean? = null
if (b == true) {
// b was not null and equal true
}
if (b == false) {
// b is false
}
if (b != true) {
// b is null or false
}
If you want to cleanly check whether a Boolean?
is true
or false
you can do:
when(b) {
true -> {}
false -> {}
}
If you want to check if it's null
you can add that (or else
) as a value in the when
:
when(b) {
true -> {}
false -> {}
null -> {}
}
when(b) {
true -> {}
false -> {}
else-> {}
}