问题描述
:key => 之间有什么区别吗?"value" (hashrocket) 和 key: "value" (Ruby 1.9) 符号?
Is there any difference between :key => "value" (hashrocket) and key: "value" (Ruby 1.9) notations?
如果没有，那么我想使用 key: "value" 表示法.是否有宝石可以帮助我从 :x => 转换为 x: 符号?
If not, then I would like to use key: "value" notation. Is there a gem that helps me to convert from :x => to x: notations?
推荐答案
是的，有区别.这些都是合法的:
Yes, there is a difference. These are legal:
h = { :$in => array }
h = { :'a.b' => 'c' }
h[:s] = 42
但这些不是:
h = { $in: array }
h = { 'a.b': 'c' } # but this is okay in Ruby2.2+
h[s:] = 42
您还可以使用 => 将任何东西用作键，这样您就可以做到这一点:
You can also use anything as a key with => so you can do this:
h = { C.new => 11 }
h = { 23 => 'pancakes house?' }
但你不能这样做:
h = { C.new: 11 }
h = { 23: 'pancakes house?' }
JavaScript 样式 (key: value) 仅在所有哈希键都是简单"符号(或多或少与 /A[a-z_] 匹配的东西)时才有用w*z/i，AFAIK 解析器对这些键使用其标签模式).
The JavaScript style (key: value) is only useful if all of your Hash keys are "simple" symbols (more or less something that matches /A[a-z_]w*z/i, AFAIK the parser uses its label pattern for these keys).
:$in 样式符号在使用 MongoDB 时会显示一些，因此如果您使用 MongoDB，最终会混合哈希样式.而且，如果您曾经使用过哈希的特定键 (h[:k]) 而不是整个哈希 (h = { ... })，您将仍然必须对符号使用冒号优先样式；对于在哈希之外使用的符号，您还必须使用前导冒号样式.我更喜欢保持一致，所以我根本不关心 JavaScript 风格.
The :$in style symbols show up a fair bit when using MongoDB so you'll end up mixing Hash styles if you use MongoDB. And, if you ever work with specific keys of Hashes (h[:k]) rather than just whole hashes (h = { ... }), you'll still have to use the colon-first style for symbols; you'll also have to use the leading-colon style for symbols that you use outside of Hashes. I prefer to be consistent so I don't bother with the JavaScript style at all.
JavaScript 风格的一些问题已在 Ruby 2.2 中得到修复.如果您的符号不是有效标签，您现在可以使用引号，例如:
Some of the problems with the JavaScript-style have been fixed in Ruby 2.2. You can now use quotes if you have symbols that aren't valid labels, for example:
h = { 'where is': 'pancakes house?', '$set': { a: 11 } }
但如果你的键不是符号，你仍然需要 hashrocket.
But you still need the hashrocket if your keys are not symbols.
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