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Why can't 'kotlin.Result' be used as a return type?
Result is a Serializable class in Kotlin. The function definition looks like this −
class Result<out T> : Serializable
This class has two properties − "isFailure" and "isSuccess".
As per the documentation, Result<T> cannot be used as a direct return type of Kotlin function. However, in this article, we will see how we can use this Result in our Kotlin programs.
// ERROR: 'kotlin.Result' cannot be used as a return type fun findUserByName(name: String): Result<User> fun foo(): Result<List<Int>> // ERROR fun foo(): Result<Int>? // ERROR var foo: Result<Int> // ERROR
Example – Kotlin.Result
sealed class myInterFace<out Success, out Failure>
data class Success<out Success>(val value: Success) : myInterFace<Success, Nothing>()
data class Failure<out Failure>(val reason: Failure) : myInterFace<Nothing, Failure>()
fun myMethod(string : String) : myInterFace<String, Exception> {
return if (string.isEmpty()) {
Failure(Exception("Error in the process"))
} else {
Success(string)
}
}
fun main(args : Array<String>) {
when(val result = myMethod("")) {
is Success -> println(result.value)
is Failure -> println(result.reason)
}
}Output
On execution, it will produce the following output −
java.lang.Exception: Error in the process
Updated on: 01-Mar-2022
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