return 来自 onComplete scala 的未来

Question

关于 forComprehension 的 练习无法编译，因为 returns Unit 而不是 Future[User]

（任务是使用 DAO 读取并使用 2 个父节点创建新用户）

我正在尝试从 onComplete return Future[User] 但失败了（returns Unit）。

def unbornUsingForComp(fatherId: String, motherId: String): Future[User] = { val fatherUser: Future[Option[User]] = usersDao.read(fatherId) val motherUser: Future[Option[User]] = usersDao.read(motherId) val combinedLastName = for { r1 <- fatherUser r2 <- motherUser } yield (r1, r2) combinedLastName.onComplete { case Success(x) => { (x._1, x._2) match { case (Some(u1), Some(u2)) => usersDao.create(User("JustRandomId", "JustRandomFirstName", u1.lastName + " - " +u2.lastName)) case _ => throw new Exception("One or more of the parents not Found") } } case Failure(_) => { throw new Exception("Exception raised inside the for comp.") } } }

Answer 1

onComplete 设计 returns Unit 执行副作用然后丢弃

// Note that the returned value of `f` will be discarded.
def onComplete[U](f: Try[T] => U)(implicit executor: ExecutionContext): Unit

您可能在寻找类似的东西

combinedLastName
  .map { x => // do stuff with x }
  .recover { case e => // handle exception }

return 来自 onComplete scala 的未来

return future from onComplete scala

scala

for-comprehension