Ruby - 获取散列值 [英] Ruby - getting value of hash

问题描述

我有一个散列，像

{：key1 => value1，：key2 => value2}

我有一个变量 k 作为'key1'或'key2'。

我想将 k 的值存入变量 v 。

如果或 case 没有任何方法可以使用来实现这一点。单线解决方案是首选。

解决方案

将密钥从字符串转换为符号，然后在哈希中查找。

  hash = {：key1 => value1，：key2 => value2} 
k ='key1'
 
 hash [k.to_sym]＃或者iow，hash [：key1]，它将返回value1
  

Rails使用这个名为 HashWithIndifferentAccess ，这在这种情况下证明是非常有用的。我知道你只用Ruby标记了你的问题，但你可以从Rails的源代码中窃取这个类的实现，以避免字符串到符号和符号在你的代码库中字符串转换。它使得该值可以通过使用符号或字符串作为键来访问。

  hash = HashWithIndifferentAccess.new（{：key1 = >value1，：key2 =>value2}）
 hash [：key1]＃value1
 hash ['key1']＃value1
  




I have a hash like

{:key1 => "value1", :key2 => "value2"}

And I have a variable k which will have the value as 'key1' or 'key2'.

I want to get the value of k into a variable v.

Is there any way to achieve this with out using if or case? A single line solution is preferred. Please help.

解决方案

Convert the key from a string to a symbol, and do a lookup in the hash.

hash = {:key1 => "value1", :key2 => "value2"}
k = 'key1'

hash[k.to_sym] # or iow, hash[:key1], which will return "value1"

Rails uses this class called HashWithIndifferentAccess that proves to be very useful in such cases. I know that you've only tagged your question with Ruby, but you could steal the implementation of this class from Rails' source to avoid string to symbol and symbol to string conversions throughout your codebase. It makes the value accessible by using a symbol or a string as a key.

hash = HashWithIndifferentAccess.new({:key1 => "value1", :key2 => "value2"})
hash[:key1]  # "value1"
hash['key1'] # "value1"

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