h = {1,2,3,4} #=>{1 =>2, 3 =>4}
h.default = 7
h[1]#=> 2
h[3]#=> 4
h[4]#=> 7
h[5]#=> 7
二。给Hash添加key-value对:
h = {} #=>{}
h.store("a",1) #=>1
h["a"] #=>1
h.fetch("a")#=>1
h["b"] = 2 #=>2
h["b"] #=>2
p h#=>{"a"=>1, "b"=>2}
三。清除Hash的key-value对:
h = {:a =>1, :b =>2}
给hash赋空值
用clear方法 (这种方法更快一点)
得到不同数据的值:%w(a b c a c d).uniq
得到各个元素出现的个数:
count_hash = {}
%w(a b c a c d).each do |item|
key = item.to_sym
if count = count_hash[key]
count_hash[key] = count + 1
else
count_hash[key] = 1
end
end