在ruby 2.2.0中创建哈希的新方法 [英] New way of creating hashes in ruby 2.2.0

问题描述

在ruby 2.2.0中，你可以这样写哈希值：

  hash = {'new_possible_style'：：of_hashes} 
 hash [：new_possible_style]＃=> ：of_hashes 
 hash ['new_possible_style']＃=>无
  

我无法理解实现这种风格的原因。如果我需要字符串作为键（例如，对于某些第三方库），我仍然必须使用旧式散列。这个'功能'的用例是什么？为什么核心开发人员添加这种风格？

在此先感谢您。

解决方案

这不是一种新的哈希表示形式，而是以一致的方式添加到1.9中的现有样式的扩展。

在1.9中，您可以这样做

  hash = {symbol_key：'value'} 
  

，您还可以使用以下语法定义 Symbol s以及其他受限制的字符：

  sym =：'a-symbol-with-dashes'
  

然而，在版本1.9到2.1中，代码

  hash = {'a-symbol-with-破折号'：'value'} 
  

不被识别为有效的语法，相反，它会得到异常 SyntaxError：（irb）：4：syntax error，unexpected'：'，expecting =>

引用在散列语法中包含 Symbol 最可能的一致性。使用短散列键语法编写Symbol文字时的选项现在与在散列之外编写相同的文字时相同（除了放置冒号的地方）

In ruby 2.2.0 you can write hashes like this:

hash = { 'new_possible_style': :of_hashes }
hash[:new_possible_style]  #=> :of_hashes
hash['new_possible_style'] #=> nil 

I cannot realise the reason for implementing this style. If I need string as key(for instance, for some third party library), I still have to use old-style hash. What the use cases for this 'feature'? Why did core-developers add this style?

Thanks in advance.

解决方案

This is not a new style of hash representation, but an extension of the existing style added in 1.9 in a consistent manner.

In 1.9, you can do this

hash = { symbol_key: 'value' }

and you can also define Symbols with otherwise-restricted characters using syntax like this:

sym = :'a-symbol-with-dashes'

However in versions 1.9 to 2.1, the code

hash = { 'a-symbol-with-dashes': 'value' }

is not recognised as valid syntax, instead it you get the exception SyntaxError: (irb):4: syntax error, unexpected ':', expecting =>

Adding support for quoted wrapping around the Symbol in the hash syntax is most likely for consistency. The options when writing a Symbol literal with the short hash key syntax are now the same as when writing the same literal outside of the hash (other than where you put the colon)

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