The docs say that to call an Obj-C method expecting an `NSNumber` you can just cast your Kotlin numb...

# multiplatform

[Sam]

The docs say that to call an Obj-C method expecting an NSNumber you can just cast your Kotlin number, but the IDE thinks "this cast will never succeed". Is that just a false positive? I've tried casting from Number, Int, Double, UInt, and it doesn't like any of them.

[Sam]

(If it is a false positive, does anyone know the magic string to @Suppress the warning?)

[jw]

What about calling .convert()

[Sam]

Hmm, I didn't know about that method before. Good to know about, but my actual variable is of type Number, which doesn't appear to have the method. I guess I could do .toDouble().convert() but that seems wasteful if the straight cast will work.

[jw]

Is it possible that multiple of your native source sets disagree on the width of the number?

[Sam]

iOS is my only native sourceset

[jw]

But that could have 32 and 64-bit variations of a type depending on the API you're calling

[Sam]

I'm gonna see if the cast succeeds at runtime as soon as I can write a test for this code

[Sam]

This is calling NSNumberFormatter from the iOS sourceset

[Sam]

expect/actual for Number formatting

[Sam]

Okay yeah the cast succeeds at runtime. The fact that it's legal is probably just not obvious to the linter.

[Sam]

After some Googling, @Suppress("CAST_NEVER_SUCCEEDS") satisfies my desire to be rid of the false warning 🙂

[Landry Norris]

If the size varies, it likes to use size_t, which gets expect/actual instead of Number. Adding the suppress is fine. You'll also need it to cast String to NSString. I'd add a comment to the suppress saying this is defined by the compiler as safe, and do it per-line so it doesn't suppress any actual issues.