Not nullable value required to call 'component1()' function of destructuring declaration initializer

Question

Is it possible to make the following code to compile in Kotlin?

val variable: String? = "string"

val (a, b) = variable?.run {
    1 to 2
}  

Answer 1

The compiler does not allow destructuring because the expression on the right-hand side is typed as a nullable Pair<Int, Int>?, and it's unclear what values a and b should get in case variable is null.

To solve this, you need to get a not-null expression after =.

There's a lot of different ways to deal with nullable values and produce a not-null value from a nullable one, see: In Kotlin, what is the idiomatic way to deal with nullable values, referencing or converting them

For example, if you want to provide fallback values for a and b, then use the ?: operator as follows:

val (a, b) = variable?.run {
    1 to 2
} ?: (0 to 0)

An alternative, for example, would be to check variable for null first:

val (a, b) = checkNotNull(variable) { "variable should never be null" }.run {
    1 to 2
}