I have a nullable Int which can be `null`, `1`, `2...

# announcements

[Lilja]

I have a nullable Int which can be null, 1, 2 and so on. It's named condition. I have a list, listOf(1,2,3,4). That's named stream. Based of on condition I would like to filter for stream, but only if it's non-null. How can I perform a filter operation if a condition either is null or a value? if(condition != null) stream.filter(it == condition) else stream is one solution I suppose but is there a cleaner way?

[Andreas Sinz]

IMO your if-version is fine. If you want you can create your own little helper function:

inline fun <T> T.runIf(predicate: Boolean, f: (T) -> T) =
    if (predicate)
        f(this)
     else
        this

myList.runIf(condition != null) {
    it.filter(it == condition)
}