在Scala中向函数发送消息 [英] Sending messages to functions in Scala

问题描述

我正在通过Bruce Tate的 七周内七种语言我很难理解他的实现 sizer.scala （Scala：第3天）。特别的，考虑下面的Singleton对象

I'm working my way through Bruce Tate's Seven Languages in Seven Weeks and am having a hard time understanding his implementation of sizer.scala (Scala: Day 3). In particular, consider the following Singleton object

object PageLoader {
    def getPageSize(url : String) = Source.fromURL(url).mkString.length
}

计算由 urls 数组给出的每个网页中的字符数。

and the following method that, using actors, calculates the number of characters in each web page given by the urls array.

def getPageSizeConcurrently() = {
    val caller = self

    for(url <- urls) {
        actor { caller ! (url, PageLoader.getPageSize(url)) }
    }

    for(i <- 1 to urls.size) {
        receive {
            case (url, size) =>
                println("Size for " + url + ": " + size)
        }
    }
}

1. 自我是指什么？ getPageSizeConcurrently ？ 自己是否可以引用某个功能？


2. 假设自己 code> getPageSizeConcurrently ，这是否被认为是在斯卡拉世界很标准？为什么要将消息发送到函数而不是对象，反之亦然？

1. What does self refer to? getPageSizeConcurrently? Is it possible for self to refer to a function?
2. Assuming that self does refer to getPageSizeConcurrently, is this considered to be pretty standard in the Scala world? Why send messages to a function instead of an object, or vice versa?

UPDATE：问题只使用自身一次，但它开始于以下 import 语句。

UPDATE: The code in question only uses self once, but it does start with the following import statements.

import scala.io._
import scala.actors._
import Actor._

查看 Scala API a>，看起来 Actor singleton对象有一个 self 方法。即使这是 self 分配给调用，虽然，我不明白为什么

Looking through the Scala API, it appears that the Actor singleton object has a self method. Even if that's the self assigned to caller, though, I don't see why the receive block would be executed.

推荐答案

在Actor配套对象上有一个自我方法。从 scaladoc ：

There is a self method on the Actor companion object. From the scaladoc:

返回当前执行的actor。

Returns the currently executing actor. Should be used instead of this in all blocks of code executed by actors.

我猜你的代码已经导入了Actor对象，并且它是你的代码正在调用的Actor对象的自我方法。这样你可以获得对你所在主actor线程的引用，并且开始获取页面大小的匿名actor可以将消息发送回你所在的线程。

I'm guessing that your code has imported the Actor object, and that it is the self method on the Actor object your code is calling. This way you get a reference to the main actor thread you're in, and the anonymous actors you start to get page size can send the message back to the thread you're in.

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