Ruby 2.2.0 RC1 发布，此版本现已提供下载。
相比 2.1.0 版本语言方面的改进： * nil/true/false
* nil/true/false objects are frozen. [Feature #8923]
* Hash literal
* Symbol key followed by a colon can be quoted. [Feature #4276]
* default argument
fixed a very longstanding bug that an optional argument was not
accessible in its default value expression. [Bug #9593]
其他更多改进内容请看发行说明。 | 
