given `data class Person(val name: String?, val ag...

# announcements

[phldavies]

given data class Person(val name: String?, val age: Int?) is there any way to have inline val Person.isValid get() = name != null && age != null allow for smart-casting when accessing `name`/`age`?

[tseisel]

I'm not sure, bur I think you could do that with the experimental contract API (the same that's used by checkNotNull or requireNotNull stdlib functions)

[rax]

yup, you can kinda do with the experimental API.
This should work:

@ExperimentalContracts
fun isValidPerson(name: String?, age: Int?): Boolean {
    contract {
        returns(true) implies (name != null)
        returns(true) implies (age != null)
    }
    return name != null && age != null
}


@OptIn(ExperimentalContracts::class)
fun test() {
    val p = Person("a", 10)
    if (isValidPerson(p.name, p.age)) {
        print(p.name.capitalize())
        print(p.age.toString())
    }
    
}

[rax]

reference https://github.com/Kotlin/KEEP/blob/master/proposals/kotlin-contracts.md

[phldavies]

Thanks