如何在处理任何数据之前测试 open-uri url 是否存在

Question

我正在尝试使用 ruby​​ (1.8.6) 中的“open-uri”处理链接列表中的内容，但是当一个链接损坏或需要身份验证时出现错误时，就会发生不好的事情

open-uri.rb:277:in `open_http': 404 Not Found (OpenURI::HTTPError)
from C:/tools/Ruby/lib/ruby/1.8/open-uri.rb:616:in `buffer_open'
from C:/tools/Ruby/lib/ruby/1.8/open-uri.rb:164:in `open_loop'
from C:/tools/Ruby/lib/ruby/1.8/open-uri.rb:162:in `catch' 

或

C:/tools/Ruby/lib/ruby/1.8/net/http.rb:560:in `initialize': getaddrinfo: no address associated with hostname. (SocketError)
from C:/tools/Ruby/lib/ruby/1.8/net/http.rb:560:in `open'
from C:/tools/Ruby/lib/ruby/1.8/net/http.rb:560:in `connect'
from C:/tools/Ruby/lib/ruby/1.8/timeout.rb:53:in `timeout'

或是

C:/tools/Ruby/lib/ruby/1.8/net/protocol.rb:133:in `sysread': An existing connection was forcibly closed by the remote host. (Errno::ECONNRESET)
from C:/tools/Ruby/lib/ruby/1.8/net/protocol.rb:133:in `rbuf_fill'
from C:/tools/Ruby/lib/ruby/1.8/timeout.rb:62:in `timeout'
from C:/tools/Ruby/lib/ruby/1.8/timeout.rb:93:in `timeout'

： 有没有办法在处理任何数据之前测试响应（url）？

代码是：

require 'open-uri'

smth.css.each do |item| 
 open('item[:name]', 'wb') do |file|
   file << open('item[:href]').read
 end
end

非常感谢

Answer 1

您可以尝试类似“

    require 'open-uri'

    smth.css.each do |item|
     begin 
       open('item[:name]', 'wb') do |file|
         file << open('item[:href]').read
       end
     rescue => e
       case e
       when OpenURI::HTTPError
         # do something
       when SocketError
         # do something else
       else
         raise e
       end
      rescue SystemCallError => e
       if e === Errno::ECONNRESET
        # do something else
       else
        raise e
       end
     end
   end

我不知道有什么方法可以测试连接而不打开它并尝试”的方法，因此挽救这些错误将是我能想到的唯一方法。需要注意的是，OpenURI::HTTPError 和 SocketError 都是 StandardError 的子类，而 Errno::ECONNRESET 是 SystemCallError 的子类。所以救援=> e 不会捕获 Errno::ECONNRESET。

Answer 2

我能够通过使用条件 if/else 语句检查“失败”操作的返回值来解决此问题：

def controller_action
    url = "some_API"
    response = open(url).read
    data = JSON.parse(response)["data"]
    if response["status"] == "failure"
        redirect_to :action => "home" 
    else
        do_something_else
    end
end