andThen

fun <T> andThen(chain: (Value) -> Result<Error, T>): Result<Error, T>

Chain two computations together

If in a computation chain the result of one computation is needed as input for another computation, andThen is there to chain the computations together.

Assume we have a result of fetching an user from a repository. We would like to send this user a notification, which in it self could fail as well.

With the following definitions.

data class User(val username: String, contactInfo: ContactInformation)

interface UserRepository {
    fun fetchByUsername(username: String)
}

fun sendNotification(user: User): Result<NotificationProblem, Record> {
    // implementation omitted
}

enum class NotificationProblem {
    CouldNotFetchUser,
    CouldNotSendNotification,
}

Sending a notification to a User amounts to

val user: Result<NotificationProblem, User> = repository.fetchByUsername('dvberkel')
val record: Result<NotificationProblem, Record> = user.andThen(::sendNotification)

Or without intermediate variables

val record = repository.fetchByUsername('dvberkel').andThen(::sendNotification)

Return

the transformed value of a Success. Keeps the error otherwise.

Parameters

chain

Provides the transformed error