What does `if (current is Set<*> && ...

# getting-started

[karelpeeters]

What does if (current is Set<*> && ...) even do? Check whether it isn't null?

[bdawg.io]

Correct

[karelpeeters]

Then just do != null, this is just obvustication ☺️.

[bj0]

why not just != null, or better yet, ?.let {}

[bdawg.io]

using is gives a smart cast

[karelpeeters]

The null check also does that.

[bdawg.io]

So instead do the following?

filterStates[requested]?.takeIf { it.isNotEmpty() }?.let { additional ->
    filters[property]?.let { current ->
        if (current.isNotEmpty()) {
            filters[property] = current.plus(additional)
        } else {
            filters[property] = additional
        }
    }
}

[karelpeeters]

I'm not a fan of nested `let`s, I'd go with != null.

[bj0]

yea I guess if you're doing if() anyway, you can combine the !=null in there to make it a little shorter

[bdawg.io]

Don’t forget that the if also contains additional conditions. Is the suggestion there to do value!!.isNotEmpty() instead of using the smart cast?

[karelpeeters]

Smart casting works within boolean expressions too:

fun foo(x: String?) {
	if(x != null && x.length == 2)
	    println("hey")
}

compiles.