What’s the correct way to transform a `NSNumber` to `kotlin.Number`? Is it just `myNsNumber as Numbe...

# kotlin-native

[kevin.cianfarini]

What’s the correct way to transform a NSNumber to kotlin.Number? Is it just myNsNumber as Number?

[ribesg]

https://kotlinlang.org/docs/native-objc-interop.html#nsnumber

[ribesg]

NSNumber can be a Boolean while Kotlin Number cannot, so NSNumber and Kotlin’s Number can’t match.

[ribesg]

You should probably not use NSNumber, the same way you should probably not use Number in Kotlin

[kevin.cianfarini]

Unfortunately I’m dealing with both NumberFormatter and NSNumberFormatter which exclusively parse to their respective platform number types

[ribesg]

You can probably make extensions to map NSNumber to kotlin types, but they aren’t all subtypes of Number

[kevin.cianfarini]

I ended up going with

checkNotNull((number as? Double) ?: (number as? Long)) {
            "$number is not either a Double or a Long."
        }

[ribesg]

Wouldn’t the first cast always work if it’s not a Boolean?

[ribesg]

I would probably use NSDecimalIsNotANumber to fail on Booleans and objCType to map to the correct Kotlin Number subclass in an extensions

[kevin.cianfarini]

Good call

[Jeff Lockhart]

As long as you know your NSNumber is not a boolean, nsNumber as Number works, as does kotlinNumber as NSNumber. Boolean `NSNumber`s will be 0 or 1 though. I've had to handle NSNumber boolean values in dictionaries/maps in another explicit format though.