Ruby EventMachine - 如何将值从EM :: Deferrable返回到主EM循环？

Question

我正在玩EventMachine已有几天了,它有一个陡峭的学习曲线恕我直言;-)我尝试通过触发HttpHeaderCrawler.query()在回调中返回一个哈希.但是我在这种情况下得到的不是hash {'http_status'=> xxx,'http_version'=> xxx},而是一个EventMachine :: HttpClient对象本身.

我想保持EM.run块干净,并想在自己的类/模块中做所有逻辑,那么如何将这样的值返回到主循环中以通过回调访问它？提前谢谢了 ;-)

#!/usr/bin/env ruby

require 'eventmachine'
require 'em-http-request'

class HttpHeaderCrawler
  include EM::Deferrable

  def query(uri)
    http = EM::HttpRequest.new(uri).get
    http.callback do
      http_header = {
        "http_status" => http.response_header.http_status,
        "http_version" => http.response_header.http_version
      }
      puts "Returns to EM main loop: #{http_header}"
      succeed(http_header)
    end
  end
end

EM.run do
  domains = ['http://www.google.com', 'http://www.facebook.com', 'http://www.twitter.com']
  domains.each do |domain|
    hdr = HttpHeaderCrawler.new.query(domain)
    hdr.callback do |header|
      puts "Received from HttpHeaderCrawler: #{header}"
    end
  end
end

此代码段产生以下输出:

Returns to EM main loop: {"http_status"=>302, "http_version"=>"1.1"}
Received from HttpHeaderCrawler: #<EventMachine::HttpClient:0x00000100d57388>
Returns to EM main loop: {"http_status"=>301, "http_version"=>"1.1"}
Received from HttpHeaderCrawler: #<EventMachine::HttpClient:0x00000100d551a0>
Returns to EM main loop: {"http_status"=>200, "http_version"=>"1.1"}
Received from HttpHeaderCrawler: #<EventMachine::HttpClient:0x00000100d56280>

Answer 1

我认为问题是#query返回http.callback,它返回http对象本身,而它应该返回self,即HttpHeaderCrawler.看看这是否有效.

def query(uri)
  http = EM::HttpRequest.new(uri).get
  http.callback do
    http_header = {
      "http_status" => http.response_header.http_status,
      "http_version" => http.response_header.http_version
    }
    puts "Returns to EM main loop: #{http_header}"
    succeed(http_header)
  end
  self
end