toDoubleOrNull

Parses the string as a Double number and returns the result or null if the string is not a valid representation of a number.

expect fun String.toDoubleOrNull(): Double?(source)

fun main() {
    val valid = "123.45"
    val invalid = "abc"

    println(valid.toDoubleOrNull())   // prints 123.45
    println(invalid.toDoubleOrNull()) // prints null
}

Source