贴一段代码

贴一段代码，其中用到了rails对Symbol的扩展，和！结尾方法的特殊含义：

E:\ruby\demo>ruby script\console
Loading development environment.
>> a = %w{word work world}
=> ["word", "work", "world"]
>> a.collect {|w| w.upcase}
=> ["WORD", "WORK", "WORLD"]
>> a
=> ["word", "work", "world"]
>> a.collect(&:upcase)
=> ["WORD", "WORK", "WORLD"]
>> a
=> ["word", "work", "world"]
>> a.collect!(&:upcase)
=> ["WORD", "WORK", "WORLD"]
>> a
=> ["WORD", "WORK", "WORLD"]