kotlin, is there a better way to check multiple nullables

Question

In kotlin it could use ?.let to only run the code block if the variable is not null. If there are multiple variables it could be done like:

v1?.let { value1 ->
    v2?.let { value2 ->
        doSomething(value1, value2)
    }
}

compare with

if (v1 != null && v2 != null){
    doSomething(v1, v2)
}

Is there a better way to do it?

https://stackoverflow.com/questions/35513636/multiple-variable-let-in-kotlin — david, Jul 26 '23 at 13:17
If you use [`konad`](https://github.com/lucapiccinelli/konad), it seems like you could do something like `::doSomething.curry().on(v1.maybe).on(v2.maybe).nullable`. — erip, Jul 26 '23 at 13:17

score 1 · Answer 1 · answered Jul 26 '23 at 13:52

1

You can make a function, pass any number of elements to it. And inside to check null or not.

fun notNull(vararg args: Any?, action: () -> Unit) {
        when (args.filterNotNull().size) {
            args.size -> action()
        }
    }

Example:

 val a = 2
 val b = "1"
 val c = "test"

 notNull(a, b, c){
           // works only when all args are not null
        }

answered Jul 26 '23 at 13:52

Ivan Abakumov

That function might read a little better if called `ifNotNull()`, or `ifNoneNull()`. – gidds Jul 26 '23 at 14:35
You would have to null-assert `!!` them inside the lambda. – Tenfour04 Jul 26 '23 at 17:25

score 0 · Answer 2 · answered Jul 26 '23 at 13:53

0

You can do something like this:

!listOf(a, b).contains(null)

Or

!listOf(a, b).any{ it == null}

But it doesn't look really good.

answered Jul 26 '23 at 13:53

Louis

2 Answers2