用string或symbol访问hash

用string或symbol访问hash

Accessing a hash with either string or symbol keys
For a normal Ruby hash, the following code is true:

x = {"key1" => "value1"}
x["key1"] #=> "value1"
x[:key1] #=> nil

What if we want to use either x[:key1] or x[“key1”] and get the same result?
Rails gives us a new Hash called HashWithIndifferentAccess that does just that. If we have a normal hash and we want to convert it into HashWithIndifferentAccess, we do the following:

x = {"key1" => "val1"}
x = x.with_indifferent_access
x[:key1] #=> "val1"
x["key1"] #=> "val1"

To instantiate a HashWithIndifferentAccess from the beginning we do the following:

x = HashWithIndifferentAccess.new #=> {}

将hash中string类型的key全部转为symbol

hash = {"apple" => "banana", "coconut" => "domino"}
hash = Hash[hash.map{ |k, v| [k.to_sym, v] }]

将hash中string类型的key全部转为symbol

hash.deep_symbolize_keys
hash.deep_symbolize_keys!

将hash中symbol类型的key全部转为string

hash.deep_stringify_keys
hash.deep_stringify_keys!