很多新手可能不能很好地理解 ruby 下的 Symbols 与 String 的差异，感谢@chenzhong 分享的一篇文章，供大家参考参考，原文地址，猛戳这里
文章最后的结论：
to use strings when:
you want to use any of string methods like #upcase, #split, #downcase etc.
you want to change/mutate the string
to use Symbols when:
symbols can't be changed at runtime. If you need something that absolutely, positively must remain constant
Places where same string is going to be repeatably used, example hash keys are pretty good candidate for symbols. so instead of string keys,hash["key"] = value. you should use symbols like this hash[:key] = value
To conclude, strings & symbols in ruby are similar but differences given above. But the main difference is that symbols are immutable & slightly more performant than strings so you should you them place where you know same string is likely to be repeated again & again.
这边博文中有两个地方不解： 第一段 script 的结果： no. of object in memory at START: 17622 number of objects in memory at END: 21624
TOTAL: number of new objects at got created during this program => 4002!!! 这里他创建了 1000 个 object，为什么相差 4002 啊？
第二段 script 的结果： TOTAL: number of new objects at got created during this program => 4002!!! 为什么只创建了一个 object，但是还是和第一段 script 的结果一样？？
求解答啊
GC.disable
start_count = ObjectSpace.count_objects
start = GC.stat[:total_allocated_object]
(1..1000).each do |i|
name = "gaurish"
puts "created a new string => #{name} in memory with object id => #{name.object_id}"
end
finish = GC.stat[:total_allocated_object]
end_count = ObjectSpace.count_objects
puts "no. of object in memory at START: #{start}"
puts "number of objects in memory at END: #{finish}"
puts "---------------------"
puts "TOTAL: number of new objects at got created during this program => #{finish - start}!!!"
p start_count
p end_count
可以跑一下自己试试，第一段的 puts 的字符串也是创建的对象，这样是 2000（1000 + 1000）
还有 1000 是 object_id 转换的 string，（3000）
剩下的 1000 应该是连接字符串时的临时对象。（4000）
第二段还是 4000 是因为多出的 1000 是 symbol 转换成的字符串。
剩下的两个估计一个是 range
另外一个就不知道了...我把循环 puts 去掉是相差1001，估计和内嵌字符串语法的内部实现有关
struct RString {
struct RBasic basic;
union {
struct {
long len;
char *ptr;
union {
long capa;
VALUE shared;
} aux;
} heap;
char ary[RSTRING_EMBED_LEN_MAX + 1];
} as;
};
#define SYMBOL_P(x) (((VALUE)(x)&~(~(VALUE)0<<RUBY_SPECIAL_SHIFT))==SYMBOL_FLAG)
RUBY_SPECIAL_SHIFT = 8
#define SYMBOL_FLAG RUBY_SYMBOL_FLAG
RUBY_SYMBOL_FLAG = 0x0e
