Kotlin - object type check against HashMap<String, String> shows warning

Question

I'm trying to check Serializable type before casting it to HashMap<String, String>. But it gives following warning;

Cannot check for instance of erased type: kotlin.collections.HashMap /* = java.util.HashMap */

Is there a way to check if Serializable is type of HashMap<String, String> then safe cast it?

params = if (it.getSerializable(ARG_PARAMS) is HashMap<String, String>) {
             it.getSerializable(ARG_PARAMS) as HashMap<String, String>
         } else null

Answer 1

Actually, you cannot check that your object has type HashMap<String, String> because type parameters are erased in runtime. I would like to suggest you just use a safe cast:

params = arguments?.getSerializable(ARG_PARAMS) as? HashMap<String, String>

Important:

It might be not clear but my code doesn't check that argument really has type HashMap<String, String>. You can pass HashMap<String, Int> and in some case, you'll get an error. In my snippet you just say to the compiler: "I know that there will be HashMap<String, String>. Just give it to me". params will be null only when there is no argument or its type differs from HashMap.