条件判断unless condition为假时执行 除非 ，否则
- .. 与…一个不包括上线，一个包括上限
- splat_splat arguments_. Splat arguments are arguments preceded by an asterisk
*. This tells the program that the method can receive one or more arguments. - You won’t become a Master Method Maker ‘til you make a mess of methods. (Say that three times fast.) :)