找不到隐式ExecutionContext。你可以通过scala

我有两个错误：

Error:(39, 20) Cannot find an implicit ExecutionContext. You might pass
an (implicit ec: ExecutionContext) parameter to your method
or import scala.concurrent.ExecutionContext.Implicits.global.
    val pipeline = sendReceive

               ^

Error:(39, 20) not enough arguments for method sendReceive: (implicit refFactory: akka.actor.ActorRefFactory, implicit executionContext: scala.concurrent.ExecutionContext, implicit futureTimeout: akka.util.Timeout)spray.client.pipelining.SendReceive.
Unspecified value parameter executionContext.
    val pipeline = sendReceive
               ^

我的代码是：

import scala.util.{Success, Failure}
import scala.concurrent.duration._
import akka.actor.ActorSystem
import akka.pattern.ask
import akka.event.Logging
import akka.io.IO
import spray.can.Http
import spray.client.pipelining._
import spray.util._
import argonaut._, Argonaut._

object test {

case class Elevation(location: Location, elevation: Double)

case class Location(lat: Double, lng: Double)

case class GoogleApiResult(status: String, results: List[Elevation])

implicit def locationFormat: CodecJson[Location] =    casecodec2(Location.apply, Location.unapply)("lat", "lng")

implicit def elevationFormat: CodecJson[Elevation] = casecodec2(Elevation.apply, Elevation.unapply)("location", "elevation")

implicit def googleApiResultFormat: CodecJson[GoogleApiResult] = casecodec2(GoogleApiResult.apply, GoogleApiResult.unapply)("status", "results")


object Main extends App {
// we need an ActorSystem to host our application in
implicit val system = ActorSystem("simple-spray-client")

// execution context for futures below
val log = Logging(system, getClass)

log.info("Requesting the elevation of Mt. Everest from Googles Elevation API...")

val pipeline = sendReceive

val responseFuture= pipeline {
  Get("http://maps.googleapis.com/maps/api/elevation/json?locations=27.988056,86.925278&sensor=false")
}

responseFuture.onComplete {
  case Success(result) =>
    println(result)
    log.info("The elevation of Mt.Everest is: {} m", result.toString.decodeOption[Elevation].get)
    shutdown()

  case Failure(error) =>
    log.error(error, "Couldn't get elevation")
    shutdown()
}
def shutdown(): Unit = {
  IO(Http).ask(Http.CloseAll)(1.second).await
  system.shutdown()
}
 }

}`

---

您需要

导入scala.concurrent.ExecutionContext.Implicits.global

作为错误指定

您可以看到

sendReceive

方法具有

隐式executionContext:scala.concurrent.executionContext

参数

--编辑--

这个答案获得了大量的视图，所以我想更新它。如您所见，这是默认的全局执行上下文，声明如下

/**
 * The implicit global `ExecutionContext`. Import `global` when you want to provide the global
 * `ExecutionContext` implicitly.
 *
 * The default `ExecutionContext` implementation is backed by a work-stealing thread pool. By default,
 * the thread pool uses a target number of worker threads equal to the number of
 * [[https://docs.oracle.com/javase/8/docs/api/java/lang/Runtime.html#availableProcessors-- available processors]].
 */
implicit lazy val global: ExecutionContextExecutor = impl.ExecutionContextImpl.fromExecutor(null: Executor)

---

它使用默认的工作池。因此，您可能需要为不同类型的并发需求提供不同类型的执行上下文

您的回答是正确的，但是@Fatih Donmez我想在didi log.info（“珠穆朗玛峰的海拔高度是：{}m”，result.toString（）.decodeOption.get）时进行求值，但是我一直都有错误：错误：（54,76）argonaut.DecodeJson[A]类型的隐式扩展从trait DecodeJson log.info中的方法SetDecodeJson开始(“珠穆朗玛峰的海拔高度是：{}m”，result.toString（）.decodeOption.get）^我想你应该为它创建另一个问题。我不能，我已经达到了我的问题极限：'（：（我不知道第二个问题。这就是我要求你创建新问题的原因。因为其他人可以帮助你解决更详细的新问题。如果我的答案解决了你的主要问题，请批准。你能发布解决方案吗？