``` fun fromActivity activity Activity Source = when activity = null amp amp activity is FooActivity gt Source FOO else gt Source UNKNOWN ``` Something tells me I don t need the null check in the above code Can I get rid of it and have the same exact behavior

Actually if you flip the ` amp amp ` expression in your code so that it looks like this `activity is FooActivity amp amp activity = null` intelliJ will even tell you that the null check is unnecessary wink

Why fix it Works as it should smile

``` fun fromActivity activity Activity Source = when activit kotlinlang #getting-started

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aphex

03/30/2017, 1:45 PM

fun fromActivity(activity: Activity?): Source = when {
                activity != null && activity is FooActivity -> Source.FOO
                else -> Source.UNKNOWN
            }

Something tells me I don’t need the null check in the above code. Can I get rid of it and have the same exact behavior?

(feel free to respond in a thread so both of our questions don’t collide)

robin

03/30/2017, 1:58 PM

Yeah, you can just remove the null check. The

is

check won't succeed if

activity

is null.

You can even have

activity

as a parameter to the

when

expression then.

aphex

03/30/2017, 2:03 PM

AWESOME :kotlin:❤️

robin

03/30/2017, 2:06 PM

Actually, if you flip the

&&

expression in your code so that it looks like this:

activity is FooActivity && activity != null

intelliJ will even tell you that the null-check is unnecessary 😉

aphex

03/30/2017, 2:10 PM

Hahah yeah, and then it suggests I introduce

activity

as an argument to when. Fix this lint-check, @jetbrains 😆

robin

03/30/2017, 2:10 PM

Why fix it? Works as it should 😄

If you mean that it doesn't catch your original situation, that's intended - there are legit cases where you actually want both checks, for example if the second check is much more expensive and you want to short-circuit it if the first check already passes, even if it was technically covered by the second one.

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