如何在Ruby中测试regexp并获取匹配的部分?

使用 $~

a = "hello123"
case a
when /^([0-9]+)([a-z]+)$/
  print $~
when /^([a-z]+)([0-9]+)$/
  print $~
else
end

将打印 MatchData 对象(MatchData是特殊变量$~的类型,是Regexp\match和Regexp\last\u match返回的对象的类型。它封装了模式匹配的所有结果,这些结果通常通过特殊变量$&,$,$`$1, $2, ( more about special vars

http://ruby-doc.org/core/classes/Regexp.html#M001202

a = "hello123"
case a
when /^([0-9]+)([a-z]+)$/
  # how to get matching values?
  puts [$~, $1, $2]
when /^([a-z]+)([0-9]+)$/
  print "regex 2 matched "
  p [$1, $2]                    # => ["hello", "123"]
  p $~.to_a                     # => ["hello123", "hello", "123"]
else
end