我撰写一份简单的文字,从德比亚网站收集一些包裹的细节。 我在处理虚拟一揽子计划时遇到问题,因为实际上一揽子计划没有与它们挂钩。

我收到以下错误信息:

undefined method `first  for nil:NilClass (NoMethodError)

专线

version = doc.css( #content h1 ).text.strip.scan( /(([^>]*))/).last.first

我试图把它当作一种条件,但这样做却不可行。

if doc.css( #content h1 ).text 
         version = doc.css( #content h1 ).text.strip.scan( /(([^>]*))/).last.first
      end

因此,我很想知道,我如何检查该物体是否为零,然后试图从中提取分号。

此处为整个文字,除非加起来。

require  rubygems 
require  nokogiri 
require  open-uri 


# additional code to make sure that we can resume after a break seamlessly
last_package = 0
File.open( lastbreak , r ) { |fptr| last_package = fptr.gets.to_i }
puts "Resuming from package:#{last_package}" if last_package != 0

# to read each package from packageslist.txt and fetch the required info
# also to store this into a file that can easily be read by the c++ program
BASE_URL = "http://packages.debian.org/stable/"

File.open( packages_list.txt , r ) do | fptr |
  while line = fptr.gets
    package_id = line.split[0].to_i
    package = line.split[1]
    dependencies = ""
    url = BASE_URL + package
    if package_id >= last_package
      doc = doc = Nokogiri::HTML(open(url))
      doc.css(".uldep a").each do |dependency|
        dependencies << dependency.text + ","
      end
      dependencies = dependencies.split( , ).uniq.join( , )
      description = doc.css( #pdesc ).text.strip
      version = ""
      unless doc.css( #content h1 ).nil?
          version = doc.css( #content h1 ).text.strip.scan( /(([^>]*))/).last.first
      end

      File.open("packages/#{package}","w") do |wfptr|
      wfptr.puts "PackageId:#{package_id}"
      wfptr.puts "Name:#{package}"
      wfptr.puts "Version:#{version}"
      wfptr.puts "Deps:#{dependencies}"
      end
      File.open("packages/#{package}.description", w ) {|wf| wf.write(description.capitalize)}

      package_id += 1
      puts "Now Processing #{package_id}"
      File.open( lastbreak , w ) { |fptr| fptr.puts "#{package_id}" }
    end
  end
end

现在错误的信息是

/Users/ccuser008/Documents/oops_project/repo/repobuilder.rb:30:in `block : undefined method `first  for nil:NilClass (NoMethodError)
    from /Users/ccuser008/Documents/oops_project/repo/repobuilder.rb:15:in `<main>