ruby - 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，但是当一个链接断开或需要身份验证时出现错误时，就会发生错误:

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

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

你可以尝试一些类似的东西

    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在不打开连接并尝试的情况下测试连接，所以挽救这些错误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 rescue => e 不会捕获 Errno::ECONNRESET。