Question

Ruby的Hash和ActiveSupport的HashWithIndifferentAccess之间有什么区别？动态哈希哪个最好？

Answer 1

下面是一个简单的例子，它将向您展示简单的 ruby hash＆amp; “ActiveSupport :: HashWithIndifferentAccess”

HashWithIndifferentAccess允许我们将哈希键作为符号或字符串

简单的Ruby Hash

$ irb
  2.2.1 :001 > hash = {a: 1, b:2}
    => {:a=>1, :b=>2} 
  2.2.1 :002 > hash[:a]
    => 1 
  2.2.1 :003 > hash["a"]
    => nil

<强>的ActiveSupport :: HashWithIndifferentAccess

2.2.1 :006 >   hash = ActiveSupport::HashWithIndifferentAccess.new(a: 1, b:2)
NameError: uninitialized constant ActiveSupport
    from (irb):6
    from /home/synerzip/.rvm/rubies/ruby-2.2.1/bin/irb:11:in `<main>'
2.2.1 :007 > require 'active_support/core_ext/hash/indifferent_access'
 => true 
2.2.1 :008 > hash = ActiveSupport::HashWithIndifferentAccess.new(a: 1, b:2)
 => {"a"=>1, "b"=>2} 
2.2.1 :009 > hash[:a]
 => 1 
2.2.1 :010 > hash["a"]
 => 1

class HashWithIndifferentAccess继承自ruby“Hash”＆amp;上面添加了特殊行为。

Answer 2

在Ruby Hash中：

hash[:key]
hash["key"]

是不同的。在HashWithIndifferentAccess顾名思义，您可以访问key。

引用官方documentation：

实现一个哈希，其中键：foo和“foo”被认为是相同。

和

内部符号在用作键时用于映射到字符串   整个书写界面（调用[] =，合并等）。这种映射   属于公共接口。例如，给定：

hash = ActiveSupport::HashWithIndifferentAccess.new(a: 1)

你是   保证密钥以字符串形式返回：

hash.keys # => ["a"]

Ruby的Hash和ActiveSupport的HashWithIndifferentAccess之间的区别

2 个答案: