A generic Kotlin wrapper class for determining the success or failure of some method

ApiResponse.kt

sealed class ApiResponse {
    class Loading(val loading: Boolean = true) : ApiResponse()
    class Success<T>(val data: T) : ApiResponse()
    class Error(val message: String) : ApiResponse()

    // For demonstration purposes only
    companion object {
        fun evaluate(response: ApiResponse) {
            when(response) {
                is ApiResponse.Loading -> {
                    when(response.loading) {
                        true -> println("Loading")
                        false -> println("Not Loading")
                    }
                }
                is ApiResponse.Success<*> -> {
                    when(response.data) {
                        is String -> println(response.data)
                        else -> println("Not a string")
                    }
                }
                is ApiResponse.Error -> {
                    println(response.message)
                }
            }
        }
    }
}

fun main(args: Array<String>) {
    var response: ApiResponse

    response = ApiResponse.Loading()
    ApiResponse.evaluate(response)
    
    response = ApiResponse.Loading(false)
    ApiResponse.evaluate(response)

    response = ApiResponse.Success("Success")
    ApiResponse.evaluate(response)

    response = ApiResponse.Error("Error")
    ApiResponse.evaluate(response)

}

/*
Output:

Loading
Not Loading
Success
Error

Process finished with exit code 0
*/