为什么编译器找不到Implicits.global导入的隐式ExecutionContext？(Why can't the compiler find implicit ExecutionC

为什么编译器找不到Implicits.global导入的隐式ExecutionContext？(Why can't the compiler find implicit ExecutionContext with Implicits.global imported?)

我有以下代码：

import java.util.concurrent.Executor import scala.concurrent.Future trait Storage { def store(location: String, content: Array[Byte])(implicit exec: Executor): Future[String] } object LocalStorage extends Storage { override def store(location: String, content: Array[Byte])(implicit exec: Executor): Future[String] = Future { ... do some stuff ... "Hello" } }

以下是测试代码：

object LocalStorageTest extends App{ import scala.concurrent.ExecutionContext.Implicits.global val testImage = AsyncWebClient get "some url" val result = testImage.flatMap{content => LocalStorage.store("logo.png",content)} val status =Await.result(result, 30 seconds) println(status) AsyncWebClient.shutDown }

每当我尝试运行代码时，我都会收到以下错误：

找不到隐式ExecutionContext。

为什么？ 范围内是不是scala.concurrent.ExecutionContext.Implicits.global？ 当此导入直接添加到LocalStorage对象时，它可以工作（！）

但我失去了改变背景的可能性。 因为我不希望每次都在全局运行此代码。 由于这是akka应用程序和“生产”运行时的一部分，因此应该在某个调度程序上运行。 仅用于测试我想在全局执行上下文中运行它。

我在这里错过了一些重要的概念，还是我的设计错了，我失去了这种灵活性？ 这个问题在哪里？！

I have the following piece of code:

import java.util.concurrent.Executor import scala.concurrent.Future trait Storage { def store(location: String, content: Array[Byte])(implicit exec: Executor): Future[String] } object LocalStorage extends Storage { override def store(location: String, content: Array[Byte])(implicit exec: Executor): Future[String] = Future { ... do some stuff ... "Hello" } }

And here comes the code for testing:

object LocalStorageTest extends App{ import scala.concurrent.ExecutionContext.Implicits.global val testImage = AsyncWebClient get "some url" val result = testImage.flatMap{content => LocalStorage.store("logo.png",content)} val status =Await.result(result, 30 seconds) println(status) AsyncWebClient.shutDown }

Whenever I try to run the code, I am getting the following error:

Cannot find an implicit ExecutionContext.

Why? Isn't scala.concurrent.ExecutionContext.Implicits.global in scope already? When this import is added directly to LocalStorage object, it works (!)

BUT I am loosing a possibility to alter the context. Since I do not want to run this code on global every time. As this is a part of an akka application and for "production" runtime it is supposed to run on some dispatcher. Just for testing I would like to run it on a global execution context.

Am I missing some important concept here or is my design wrong that I am loosing such flexibility? Where is the issue?!

最满意答案

ExecutionContext与Executor 。 你应该让方法接受一个implicit exec: ExecutionContext （ scala.concurrent.ExecutionContext ）然后它将按你的预期运行。

An ExecutionContext is not the same thing as an Executor. You should make the method accept an implicit exec: ExecutionContext (scala.concurrent.ExecutionContext) and then it will behave as you expect.