Pass a sealed class as function argument android

Question

I have a sealed class which represents the Retrofit Response of my API.

sealed class NetworkResponse<out T : Any, out U : Any> {
   
    data class Success<T : Any>(val body: T) : NetworkResponse<T, Nothing>()

    data class ApiError<U : Any>(val body: U, val code: Int) : NetworkResponse<Nothing, U>()

    data class NetworkError(val error: IOException) : NetworkResponse<Nothing, Nothing>()

    data class UnknownError(val error: Throwable?) : NetworkResponse<Nothing, Nothing>()
}

So now i want to create a function that handles all the errors of a failed request. I want to have only one argument that represents either ApiError or NetworkError or UnknownError

fun networkErrorHanlder(mError: <what_should_i_put_here??>) {
   // check if error is Api or Network or Unknown and do stuff...
}

What should be the type of the argument?

score 2 · Accepted Answer · answered Aug 04 '20 at 00:49

Since you care only about ApiError, NetworkError and UnknownError, which all derive from NetworkResponse but don't use the first generic type, you can specify that you don't care about it using * (Actually, depending on what you want to do with mError, you can replace U with * too - that is the case in the code below, but I introduced U just in case). In that case, you should accept a NetworkReponse:

fun <U : Any> networkErrorHanlder(mError: NetworkResponse<*, U>) {
    when(mError) {
        is NetworkResponse.ApiError ->
            print("Api stuff: ${mError.body}")
        is NetworkResponse.NetworkError ->
            print ("Network stuff: ${mError.error}")
        is NetworkResponse.UnknownError ->
            print("Unknown: ${mError.error}")
        else -> print("It must've been a Success...")
    }
}

Pass a sealed class as function argument android

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