blocks|key|69596|text|gsub的第二个参数应该是字符串，而不是正则表达式(参见docs)。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|69597|执行以下操作：|69598|x.gsub(/([0-9]{2})-%2B([0-9]{2})-%2B([0-9]{4})/,'\3-\2-\1')|code-block|syntax|javascript|69599|请注意，第二个参数使用'replacement+string'而不是/replacement+string/。|style|CODE|69600|entityMap|0|LINK|mutability|MUTABLE|url|http://ruby-doc.org/core-2.0/String.html#method-i-gsub^0|S|4|0|0|0|0|B|K|Y|K|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|6|7|10|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|11|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|12|8|@$A|13|B|14|M|N]|$A|15|B|16|M|N]]|9|@]|C|$]]|$1|O|3|-4|5|6|7|17|8|@]|9|@]|C|$]]]|P|$Q|$5|R|S|T|C|$U|V]]]]

The second parameter for the gsub should be a string, not a regex (see the <a href="http://ruby-doc.org/core-2.0/String.html#method-i-gsub" rel="nofollow">docs</a>).

Do:

<pre><code>x.gsub(/([0-9]{2})-+([0-9]{2})-+([0-9]{4})/,'\3-\2-\1')
</code></pre>

Note that the second parameter uses <code>'replacement string'</code> instead of <code>/replacement string/</code>.

blocks|key|69667|text|使用'分隔第二个gsub参数(替换字符串)，而不是/|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|69668|entityMap^0|2|1|8|4|P|1|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|O|8|@]|D|@]|E|$]]]|G|$]]

Use <code>'</code> to delimit your second <code>gsub</code> parameter (the replacement string), instead of <code>/</code>

blocks|key|69673|text|无正则表达式：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|69674|str+=+"DDMMYYYY"
p+new_str+=+str[4..7]+<<+str[2..3]+<<+str[0..1]
#=>+"YYYYMMDD"|code-block|syntax|javascript|69675|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

No regex:

<pre><code>str = "DDMMYYYY"
p new_str = str[4..7] &lt;&lt; str[2..3] &lt;&lt; str[0..1]
#=&gt; "YYYYMMDD"
</code></pre>

blocks|key|858176|text|我会选择Date::strptime和Date#strftime|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|858177|dates+=+%25w[12122012+10121012+12032013]
#=>+["12122012",+"10121012",+"12032013"]

dates.each+do+%7Cdate_str%7C
++date+=+Date.strptime(date_str,+'%25d%25m%25Y')
++puts+date.strftime('%25Y+%25m+%25d')
end

#+2012+12+12
#+1012+12+10
#+2013+03+12|code-block|syntax|javascript|858178|entityMap|0|LINK|mutability|MUTABLE|url|http://ruby-doc.org/stdlib-2.0/libdoc/date/rdoc/Date.html#method-c-_strptime|1|http://ruby-doc.org/stdlib-2.0/libdoc/date/rdoc/Date.html#method-i-strftime^0|4|E|J|D|4|E|0|J|D|1|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@$9|Z|A|10|1|11]|$9|12|A|13|1|14]]|E|$]]|$1|F|3|G|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]|S|$5|N|O|P|E|$Q|T]]]]

I'd go with <a href="http://ruby-doc.org/stdlib-2.0/libdoc/date/rdoc/Date.html#method-c-_strptime" rel="nofollow"><code>Date::strptime</code></a> and <a href="http://ruby-doc.org/stdlib-2.0/libdoc/date/rdoc/Date.html#method-i-strftime" rel="nofollow"><code>Date#strftime</code></a>:

<pre><code>dates = %w[12122012 10121012 12032013]
#=&gt; ["12122012", "10121012", "12032013"]

dates.each do |date_str|
 date = Date.strptime(date_str, '%d%m%Y')
 puts date.strftime('%Y %m %d')
end

# 2012 12 12
# 1012 12 10
# 2013 03 12
</code></pre>

blocks|key|2193209|text|我认为值得补充的是，虽然上面的答案是正确的，但它们没有解决OP得到的错误。如果第二个参数是正则表达式，则此错误不是问题。事实上，在上面的例子中，ruby从未真正调用过gsub方法，因为第二个参数中的正则表达式不会被解析。反斜杠后跟任何数字都会导致此错误。它是无效的正则表达式。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2193210|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I think it's worth adding that while the above answers are correct they don't address the error that the OP was getting. This error is not an issue with the second parameter being a regular expression. In fact in the above case ruby never actually calls the gsub method as the regular expression in the second parameter won't parse. A backslash followed by any number will cause this error. It's an invalid regular expression.

My current code is intended to go through an enormous .csv file and reformat certain dates to an SQL Datetime friendly format. They are currently DDMMYYYY, I want them as YYYYMMDD, and this is the approach I've taken (lifted from a different SO question):

<pre><code>CSV.foreach('file.csv') do |x|
if x[0] == "1"
 x.gsub(/([0-9]{2})-+([0-9]{2})-+([0-9]{4})/,/\3-\2-\1/)

else
end
</code></pre>

This throws the error "invalid backref number/name".

Docs tell me I can avoid this by defining the groups with <code>?&lt;name&gt;</code> and backreferencing them with <code>\k&lt;name&gt;</code>, but all my attempts to do so have ended in failure. Could someone show me how it's supposed to look, or provide an alternate solution?

Ruby regexp throws invalid backref number/name error

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我当前的代码旨在遍历一个庞大的.csv文件，并将某些日期重新格式化为SQL Datetime友好的格式。它们当前是DDMMYYYY，我希望它们是YYYYMMDD，这是我采取的方法(取自一个不同的SO问题)：CSV.foreach('file.csv') do |x|if x[0] == "1"    x.gsub(/(...

问Ruby regexp抛出无效的backref编号/名称错误
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