Ruby中的Symbol

A symbol is an identifier whose first character is a colon ( : ), so :this is a symbol and so is :that.
symbol是以：开头的。
A symbol is not: it is not a string, it is not a constant and it is not a variable. A symbol is, quite simply, an identifier with no intrinsic meaning other than its own name.
symbol不是字符串，不是常量，不是变量，它只是一个符号，来表示它自己的名字

同一个symbol在不同的上下文中是一样的.

顺便提一句，值相同的Fixnum的哦bject_id也是一样的

#from Ruby docmodule One  class Fred  end  $f1 = :Fredendmodule Two  Fred = 1  $f2 = :Fredenddef Fred()end$f3 = :Fred$f1.object_id   #=> 2514190$f2.object_id   #=> 2514190$f3.object_id   #=> 2514190