Add String?.shouldBeInteger([Int]): Int

[SerVB]

Hi! I frequently do something like

val int = str?.toIntOrNull()
int.shouldNotBeNull()

// work with int

So I've defined shouldBeInteger function in my project and now it's like

val int = str.shouldBeInteger()

// work with int

Is it OK to add this function to the repo?

[sksamuel]

Great idea, can we use contracts to smart case the type ?

[SerVB]

You mean a contract for non-null like the following?

@OptIn(ExperimentalContracts::class)
fun String?.shouldBeInteger(radix: Int = 10): Int {
    contract {
        returns() implies (this@shouldBeInteger != null)
    }

    return when (this) {
        null -> throw failure("String is null, but it should be integer.")

        else -> when (val integer = this.toIntOrNull(radix)) {
            null -> throw failure("String '$this' is not integer, but it should be.")

            else -> integer
        }
    }
}

It doesn't make much sense to me because after this operation I don't work with the initial string. However, if you think it could be useful, I can add it.

[sksamuel]

Not just null, but I wonder if we can use smart cast from string to int ? a.shouldBeInt() a % 3 shouldBe 1

…

On Sat, 28 Mar 2020 at 14:18, Sergei Bulgakov ***@***.***> wrote: You mean a contract for non-null like the following? @OptIn(ExperimentalContracts::class)fun String?.shouldBeInteger(radix: Int = 10): Int { contract { returns() implies ***@***.*** != null) } return when (this) { null -> throw failure("String is null, but it should be integer.") else -> when (val integer = this.toIntOrNull(radix)) { null -> throw failure("String '$this' is not integer, but it should be.") else -> integer } } } It doesn't make much sense to me because after this operation I don't work with the initial string. However, if you think it could be useful, I can add it. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#1315 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAFVSGTF7XROLXTUFU77EDDRJZEQLANCNFSM4LVSOIVQ> .

[SerVB]

I think smart casting to Int is impossible here because there is still a String in a after this function returns.

But smart cast from String? to String is possible.

[sksamuel]

Ok makes sense

…

On Sat, 28 Mar 2020, 14:22 Sergei Bulgakov, ***@***.***> wrote: I think smart casting to Int is impossible here because there is still a String in a after this function returns. But smart cast from String? to String is possible. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#1315 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAFVSGQJJ5G7DSGCBZRFM53RJZE6XANCNFSM4LVSOIVQ> .

[SerVB]

Added the contract.