Hi, say after send a request , the response have two type , when success

@Serializable
data class Success(
    var code: Int, // maybe 0
    var content: String,
) {}

while fail:

@Serializable
data class Fail(
    var code: Int, // maybe 1
    var err: String,
) {}

I wanna know what is the elegant way to handle the two situation?

val res:Response = sendRequest<what should I put here?>()
// and how should I define Response?
if(res instanceOf Success){...} else if (res instanceOf Fail){...}

and is the code above a proper way ?

I think you can use railway oriented programming here