如何将List[zio.Task[List[A]转换为zio.Task[[List[A]] ]

Question

我需要处理一组Ids并以zio.Task[ListRelevantReadingRow]的形式返回结果

def getBaselinesForRequestIds(baseLineReqIds: Set[String]): Task[List[RelevantReadingRow]] =
  dynamoConnection
    .run(
      table.getAll("baseline_req_id" in baseLineReqIds)
    )
    .flatMap(_.toList.separate match {
      case (err :: _, _)           => ZIO.fail(new Throwable(describe(err)))
      case (Nil, relevantReadings) => ZIO.succeed(relevantReadings)
    })

上面的代码可以工作，但我需要将它们作为mutch处理成25个元素的批次。我试过了，但是我得到了一个zio.Task列表

def getBaselinesForRequestIds(baseLineReqIds: Set[String]): Task[List[RelevantReadingRow]] = {
    val subSet = baseLineReqIds.grouped(25).toList
    val res = for {
      rows <- subSet.map(reqIds => dynamoConnection
        .run(
          table.getAll("baseline_req_id" in reqIds)
        ).flatMap(e => e.toList.separate match {
        case (err :: _, _) => ZIO.fail(new Throwable(describe(err)))
        case (Nil, relevantReadings) => ZIO.succeed(relevantReadings)
      }))
    } yield rows
    res // this is List[zio.Task[List[RelevantReadingRow]]]
  } 

我不知道如何转换回zio.Task[ListRelevantReadingRow]

有服用吗？

Answer 1

你可以用ZIO.collectAll把ListTask转换成TaskList，我以为是ZIO.sequence.也许我被猫弄糊涂了.

下面的示例适用于Zio2

package sample

import zio._

object App extends ZIOAppDefault {
  case class Result(value: Int) extends AnyVal

  val data: List[Task[List[Result]]] = List(
    Task { List(Result(1), Result(2)) },
    Task { List(Result(3)) }
  )

  val flattenValues: Task[List[Result]] = for {
    values <- ZIO.collectAll { data }
  } yield values.flatten

  val app = for {
    values <- flattenValues
    _      <- Console.putStrLn { values }
  } yield()

  def run = app
}

特别是你的样本..。假设“分离”只是收集一些错误的扩展方法(返回错误列表和结果列表的元组)，忽略方法“描述”将错误转换为可抛出的错误

https://scastie.scala-lang.org/jgoday/XKxVP2ECSFOv4chgSFCckg/7

package sample

import zio._


object App extends ZIOAppDefault {
  class DynamoMock {
    def run: Task[List[RelevantReadingRow]] = Task {
      List(
        RelevantReadingRow(1),
        RelevantReadingRow(2),
      )
    }
  }

  case class RelevantReadingRow(value: Int) extends AnyVal

  implicit class ListSeparate(list: List[RelevantReadingRow]) {
    def separate: (List[String], List[RelevantReadingRow]) =
      (Nil, list)
  }

  def getBaselinesForRequestIds(baseLineReqIds: Set[String]): Task[List[RelevantReadingRow]] = {
    val dynamoConnection = new DynamoMock()
    val subSet = baseLineReqIds.grouped(25).toList
    val res: List[Task[List[RelevantReadingRow]]] = for {
      rows <- subSet.map(reqIds => dynamoConnection
        .run.flatMap(e => e.toList.separate match {
          case (err :: _, _) => ZIO.fail(new Throwable(err))
          case (Nil, relevantReadings) => ZIO.succeed(relevantReadings)
        }))
    } yield rows

    for {
      rows <- ZIO.collectAll(res)
    } yield rows.flatten
  }

  val app = for {
    values <- getBaselinesForRequestIds(Set("id1", "id2"))
    _      <- Console.putStrLn { values }
  } yield()

  def run = app
}

Answer 2

因此，这里有一个基于@jgoday答案的替代解决方案

def getBaselinesForRequestIds(baseLineReqIds: Set[String]): Task[List[RelevantReadingRow]] =
    for {
      values <- ZIO.foreachPar(baseLineReqIds.grouped(25).toList) {
        reqIds =>
          dynamoConnection
            .run(
              table.getAll("baseline_req_id" in reqIds)
            ).flatMap(e => e.toList.separate match {
            case (err :: _, _) => ZIO.fail(new Throwable(describe(err)))
            case (Nil, relevantReadings) => ZIO.succeed(relevantReadings)
          })
      }
    } yield values.flatten