获取哈希的所有键或值

{foo: 'bar', biz: 'baz'}.keys   # => [:foo, :biz]
{foo: 'bar', biz: 'baz'}.values # => ["bar", "baz"]
{foo: 'bar', biz: 'baz'}.to_a   # => [[:foo, "bar"], [:biz, "baz"]]
{foo: 'bar', biz: 'baz'}.each   #<Enumerator: {:foo=>"bar", :biz=>"baz"}:each>