Ruby符号与Hashes中的字符串 [英] Ruby Symbols vs Strings in Hashes

问题描述

我有这个散列：

  {
title=>海军进行呼气测试所有船只上的机器，
url=>http://feeds.washingtonpost.com/click.php?id=a67626ca64a9f1766b8ba425b9482d49
} 
  
 
 
 $ b $ p 
 
 
 
 $  hash [ ：url] == nil 
  

和

  hash ['url'] ==http://feeds.washingtonpost.com/click.phdo?i=a67626ca64a9f1766b8ba425b9482d49
  

为什么？它不应该与它一起工作吗？

解决方案

由于符号与字符串不同：

 ：url =='url'＃=>假
  

作为散列键他们会有所不同。也许你在Rails中看到过这种行为？ Ruby on Rails使用 HashWithIndifferentAccess 将所有内容映射到字符串内部，因此您可以这样做：

  h = HashWithIndifferentAccess.new 
h ['url'] ='http://www.google.com/'
h [：url] ＃=> 'http://www.google.com/'
  




I have this hash:

{
  "title"=>"Navy to place breath-test machines on all its ships", 
  "url"=>"http://feeds.washingtonpost.com/click.phdo?i=a67626ca64a9f1766b8ba425b9482d49"
} 

It turns out that

hash[:url] == nil

and

hash['url'] == "http://feeds.washingtonpost.com/click.phdo?i=a67626ca64a9f1766b8ba425b9482d49"

Why? Shouldn't it work with either?

解决方案

Since a symbol is not the same as a string:

:url == 'url' #=> false

As hash keys they would be different. Perhaps you have seen this behavior in Rails? Ruby on Rails uses HashWithIndifferentAccess which maps everything to a String internally, so you can do this:

h = HashWithIndifferentAccess.new
h['url'] = 'http://www.google.com/'
h[:url] #=> 'http://www.google.com/'

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