我有一个 Future[Either[A, B]]以及提供 Future[C] 的函数来自 B .

我需要转换 Future[Either[A, B]]至 Future[Either[A, C]] .

有没有直接获取Future[Either[A, C]]的方法而不是 Future[Either[A, Future[C]]] ?

我正在考虑类似的事情:

val eventuallyInitialValue: Future[Either[A, B]] = ??? 
val result: Future[Either[A, C]] = for { 
  e: Either[A, B] <- initialValue 
  c: C <- service.getValue(e.right) 
} yield e.right.map(_ => c) 

请您参考如下方法:

这就是我想出的:

type B = Int 
type A = String 
type C = Long 
val eitherF: Future[Either[A, B]] = ??? 
def f(b: B): Future[C] = ??? 
 
val mapped: Future[Either[A, C]] = eitherF.flatMap { 
  case Left(a) => 
    Future.successful(Left(a)) 
  case Right(b) => 
    f(b).map(Right(_)) 
}