Ruby：散列键的属性

irb(main):001:0> h =  { }
=> {}
irb(main):002:0> a=[1,2,3]
=> [1,3]
irb(main):003:0> a.object_id
=> 69922343540500


irb(main):004:0> h[a] = 12          #Hash with the array as a key
=> 12
irb(main):005:0> a << 4             #Modified the array
=> [1,3,4]
irb(main):006:0> a.object_id        #Object id obviously remains the same.
=> 69922343540500
irb(main):007:0> h[a]               #Hash with the same object_id now returns nil.
=> nil
irb(main):008:0> h                  #Modified hash
=> {[1,4]=>12}
irb(main):009:0> h[[1,4]]       #Tried to access the value with the modified key -
=> nil


irb(main):011:0> h.each { |key,value| puts "#{key.inspect} maps #{value}" }
[1,4] maps 12
=> {[1,4]=>12}

现在,当我遍历哈希时,可以识别密钥和值之间的映射.

有人可以解释一下ruby hash的这种行为以及散列键的属性是什么.

1)正如我上面提到的,object_id没有改变 – 那么为什么值设置为nil.

2)是否有任何可能的方法,以便我可以从散列’h’返回值’12’,因为上面提到的h [[1,4]]返回nil.