Generate IV from key

[squinney]

I'm trying to port an Android method that uses SecretKeySpec and Cipher classes to take a 256 bit key and instantiate a Cipher class with AES/CBC/PKCS5PADDING transformation, from which a non-random 128 bit IV can be returned. I'm not seeing how to do the same in any iOS implementation - can you advise?
val key: SecretKey = SecretKeySpec(<key>, "AES")
val cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING")
cipher.init(Cipher.ENCRYPT_MODE, key)
val iv = Hex.bytesToStringUppercase(cipher.iv)