找到了一个 workaround

old = :+
new = :plus__
Fixnum.class_eval "alias #{new} #{old}"

确实 alias_method 可以传变量，多谢指点！

知道对 method 使用的，比如下面这段代码，想把 :old_plus 和 :+ 先赋给变量，再来使用 alias，就会报错。

class Fixnum
  alias :old_plus :+
  def +(value)
    self.old_plus(value).old_plus(1)
  end
end

new --> new_name 一样不行。

monkey patch 能有效吗？alias 是 ruby 的 keyword，不是 method。

你的运行环境是怎样的呀？

因为例子中的代码改写了 + 的结果为正确结果 +1，因此当定义完 + （method）后，C:/Ruby22/lib/ruby/site_ruby/2.2.0/rbreadline.rb 里的表达式做加法运算时出现了对数组索引越界的错误。但是为何有些环境下就正常运行呢（比如 Linux）？

我的出错信息是这样的。当前在 Windows 上使用的是 ruby 2.2.6, 试过 ruby 2.4.2, 结果是一样的。是不是哪里配置不对？

irb(main):001:0> class Fixnum
irb(main):002:1> alias :old_plus :+
irb(main):003:1* def +(value)
irb(main):004:2> self.old_plus(value).old_plus(1)
irb(main):005:2> end
irb(main):006:1> end
=> :+
C:/Ruby22/lib/ruby/site_ruby/2.2.0/rbreadline.rb:1716:in `block in expand_prompt': no implicit conversion of nil into St
ring (TypeError)
        from C:/Ruby22/lib/ruby/site_ruby/2.2.0/rbreadline.rb:1696:in `each'
        from C:/Ruby22/lib/ruby/site_ruby/2.2.0/rbreadline.rb:1696:in `expand_prompt'
        from C:/Ruby22/lib/ruby/site_ruby/2.2.0/rbreadline.rb:1784:in `rl_expand_prompt'
        from C:/Ruby22/lib/ruby/site_ruby/2.2.0/rbreadline.rb:1809:in `rl_set_prompt'
        from C:/Ruby22/lib/ruby/site_ruby/2.2.0/rbreadline.rb:4821:in `readline'
        from C:/Ruby22/lib/ruby/site_ruby/2.2.0/readline.rb:45:in `readline'
        from C:/Ruby22/lib/ruby/2.2.0/irb/input-method.rb:150:in `gets'
        from C:/Ruby22/lib/ruby/2.2.0/irb.rb:469:in `block (2 levels) in eval_input'
        from C:/Ruby22/lib/ruby/2.2.0/irb.rb:623:in `signal_status'
        from C:/Ruby22/lib/ruby/2.2.0/irb.rb:468:in `block in eval_input'
        from C:/Ruby22/lib/ruby/2.2.0/irb/ruby-lex.rb:188:in `call'
        from C:/Ruby22/lib/ruby/2.2.0/irb/ruby-lex.rb:188:in `buf_input'
        from C:/Ruby22/lib/ruby/2.2.0/irb/ruby-lex.rb:103:in `getc'
        from C:/Ruby22/lib/ruby/2.2.0/irb/slex.rb:205:in `match_io'
        from C:/Ruby22/lib/ruby/2.2.0/irb/slex.rb:75:in `match'
        from C:/Ruby22/lib/ruby/2.2.0/irb/ruby-lex.rb:282:in `token'
        from C:/Ruby22/lib/ruby/2.2.0/irb/ruby-lex.rb:264:in `lex'
        from C:/Ruby22/lib/ruby/2.2.0/irb/ruby-lex.rb:235:in `block (2 levels) in each_top_level_statement'
        from C:/Ruby22/lib/ruby/2.2.0/irb/ruby-lex.rb:231:in `loop'
        from C:/Ruby22/lib/ruby/2.2.0/irb/ruby-lex.rb:231:in `block in each_top_level_statement'
        from C:/Ruby22/lib/ruby/2.2.0/irb/ruby-lex.rb:230:in `catch'
        from C:/Ruby22/lib/ruby/2.2.0/irb/ruby-lex.rb:230:in `each_top_level_statement'
        from C:/Ruby22/lib/ruby/2.2.0/irb.rb:485:in `eval_input'
        from C:/Ruby22/lib/ruby/2.2.0/irb.rb:395:in `block in start'
        from C:/Ruby22/lib/ruby/2.2.0/irb.rb:394:in `catch'
        from C:/Ruby22/lib/ruby/2.2.0/irb.rb:394:in `start'
        from C:/Ruby22/bin/irb:11:in `<main>'

但是在 Linux 上试了 ruby 1.8.7，功能正常，输出如下，和上面的输出相比，=>:+ 变成了 => nil, 这又是什么原因？

irb(main):001:0> class Fixnum
irb(main):002:1> alias :old_plus :+
irb(main):003:1* def +(value)
irb(main):004:2> self.old_plus(value).old_plus(1)
irb(main):005:2> end
irb(main):006:1> end
=> nil

谢谢指点！ 通过对文档里的 inspect 方法的返回值（AClass.method 或者 AClass#method）进行判断，可以用来区分 class method 还是 instance method。 但是，如果要判断 public 还是 private，似乎没提供直接的方法。

经过验证，这段代码是查找类似 .dir_a 这样的以 dot 开头且跟有名字的目录，而对 . 目录本身不起作用。

谢谢给位的指点！

特别欣赏这种授之以渔的解答 那行代码里的意思是寻找以 . 开头的 directory，那么 . 目录（当前目录）能被搜到吗？还是一定要 . 开头的有名字的目录，比如 .dir_a。

就是想找在哪里定义了这种用法。无奈不知从何下手，多谢指点！ 顺便问一下，为何将#4 里的那段代码删除，也不会影响运行结果？每个目录下应该都有 . 目录的呀。

试了下原帖里的代码，即便把下面这段都去掉，也不会影响运行结果 所以很难确定 ?. 就等同于 "." :

if File.basename(path)[0] == ?.
  Find.prune       # Don't look any further into this directory.
else
  next
end

原帖代码

require 'find'
puts ""
puts "-----------------------File Search-----------------------------------"
puts ""
print "Enter the search path    : "
searchpath = gets
searchpath = searchpath.chomp
puts ""
print "Enter the search pattern : "
pattern = gets
pattern = pattern.chomp
puts"----------------------------------------------------------------------"
puts "Searching in " + searchpath + " for files matching pattern " + pattern
puts"----------------------------------------------------------------------"
puts ""
 Find.find(searchpath) do |path|
   if FileTest.directory?(path)
     if File.basename(path)[0] == ?.
       Find.prune       # Don't look any further into this directory.
     else
       next
     end
   else
     if File.fnmatch(pattern,File.basename(path))
       puts  "Filename     : " +  File.basename(path)
       s = sprintf("%o",File.stat(path).mode)
       print "Permissions  : "
       puts s
       print "Owning uid   : "
       puts File.stat(path).uid
       print "Owning gid   : "
       puts File.stat(path).uid
       print "Size (bytes) : "
       puts File.stat(path).size
       puts "---------------------------------------------------"
     end
   end
 end

谢谢指点！ 关于这样的用法？. 在哪里有文档说明吗？

解决了。

ruby_config() { ruby1.9 -rrbconfig -e "puts Config::CONFIG['$1']" | grep -v "ruby 1.9.0"; } gcc embed.c -o embed \ -I ruby_config rubyhdrdir \ -I ruby_config rubyhdrdir/ruby_config arch \ -L ruby_config libdir \ ruby_config LDFLAGS \ ruby_config LIBS \ ruby_config LIBRUBYARG

参考 http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/14864 http://blog.csdn.net/wu4long/article/details/4048759

为啥我发不了贴