Hey Guys, I have enum class and I am mapping by value, when I am return Enum value it always complai...

# android

[Vivek Modi]

Hey Guys, I have enum class and I am mapping by value, when I am return Enum value it always complain about null issue.

enum class ConversationStatus(val status: String) {
    OPEN("open"),
    CLOSED("closed");

    companion object {
        private val mapByStatus = values().associateBy(ConversationStatus::status)
        fun fromType(status: String): ConversationStatus {
            return mapByStatus[status]
        }
    }
}

How can i avoid this ?

[Grégory Lureau]

Kotlin can't enforce that all possible strings are mapped here, you could send a string not mapped to anything, so either you consider it's not the enum job to crash and returns a nullable value, either you consider it should never happen and you can assert/throw when it happens.

[Grégory Lureau]

fun fromType(status: String): ConversationStatus {

return mapByStatus[status]!!

}

or any other more verbose way if you prefer:

fun fromType(status: String): ConversationStatus {

val cv = mapByStatus[status]

assert(cv != null) { "ConversationStatus.fromType cannot handle $status"}

return cv

}

[Damian Zawadzki]

or just

fun fromType(status: String): ConversationStatus {
  return requireNotNull(mapByStatus[status])
}

[Vivek Modi]

thanks @Damian Zawadzki, what does requireNotNull mean?

[Vivek Modi]

@Grégory Lureau great anwser

[Damian Zawadzki]

it ensures that value is not null and returns not null variable that you provide as parameter. If parameter somehow null then exception is thrown.

[Vivek Modi]

okk great

[Vivek Modi]

thanks

[Damian Zawadzki]

and additionally the check in requireNotNull ensures that parameter outside will be ensured as not nullable:

fun a(a: String?){
        requireNotNull(a)
        a.length //no error without ? after a
    }

by a contract mechanism inside.

[Vivek Modi]

okkk

[bezrukov]

or

fun fromType(status: String): ConversationStatus {
  return mapByStatus.getValue(status)
}