从字符串中取出日期
我的问题如下：
我有一个包含日期和其他数据的字符串数组。我的日期将采用以下几种格式之一：
- dd/mm/yyyy
- dd/mm/yy
- mm/yy
- d/m/yy
- yyyy
- yy
有没有办法在字符串中搜索适合字符串中该模式的数字？
另外，如果我可以检查 dd 是否在 1 到 31 之间（包含 1 和 31）等，那就太好了，但如果我事后必须这样做也不会那么糟糕。
My problem is as follows:
I have an array of strings that contain dates and other data. My date will have one of several formats:
- dd/mm/yyyy
- dd/mm/yy
- mm/yy
- d/m/yy
- yyyy
- yy
Is there a way to search a string for numbers that fit that pattern in the string?
In addition, it would be nice if I could check if the dd is between 1 and 31 inclusive etc, but it would not be so bad if I had to do that afterwards.
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评论（1）
其中每一个都对应一个正则表达式。
以下是每个的正则表达式：
\b(?:[012][1-9]|3[01])/(?:0[1-9]|1[012])/\d{4}\b\b(?:[012][1-9]|3[01])/(?:0[1-9]|1[012])/\d{2}\b\b(?:0[1-9]|1[012])/\d\d\b\b[1-9]/[1-9]/\d\d\b\b\d{4}\b\b\d\d\b当然，您可以通过不同的方式将它们组合在一起。您甚至可以制作一个超级正则表达式。
不过，最后一个相当有趣。我可以想象这样一种情况，您的文本中可能有一个普通的旧数字，例如
42，它实际上可能与年份不对应。不过我想你可以对其进行后处理。快乐的调整。
ADDENDUM
回答评论中的一些问题：
是的，它在字符串的开头和结尾有效，因为
\b是单词边界< /em>，其中包括从单词字符（字母、数字和下划线）到非单词字符的所有转换，反之亦然，包括字符串的开头和结尾。要查看测试，请参阅此处：http://jsfiddle.net/wRufK/。是的，我知道这是用 JavaScript 而不是 C# 编写的，但 jsfiddle 是显示实际代码的一种非常方便的方法。但还是有区别的——在 C# 中，我们使用
Regex.match，而 JavaScript 正则表达式有额外的反斜杠来转义内部正斜杠。indexOf可能过度杀伤力，具体取决于应用程序。如果要查找所有匹配项，请参阅 http://msdn.microsoft.com/ en-us/library/twcw2f1c.aspx 有关重复匹配的信息。您还可以修改用于捕获的正则表达式。由于您的日期可以采用上述任何形式，也可能采用其他形式，因此单个正则表达式可能更可取。一个非常灵活的日期查找器在这里： http://www.regular-expressions.info/dates.html 。您可能需要考虑它，而不是固定一个精确的集合。
Each of these corresponds to a regex.
Here are regexes for each:
\b(?:[012][1-9]|3[01])/(?:0[1-9]|1[012])/\d{4}\b\b(?:[012][1-9]|3[01])/(?:0[1-9]|1[012])/\d{2}\b\b(?:0[1-9]|1[012])/\d\d\b\b[1-9]/[1-9]/\d\d\b\b\d{4}\b\b\d\d\bOf course, you can combine these together in different ways. You can even make one super regex.
The last one is rather interesting, though. I can imagine a case where you might have a plain old number in your text, like
42that might not actually correspond to a year. Still I guess you can postprocess that.Happy regexing.
ADDENDUM
To answer some questions in the comments:
Yes it works at the beginning and the end of the string, because
\bis a word boundary, which includes all transitions from word characters (letters, digits, and underscores) to non-word characters and vice-versa, including the beginning and ending of the string.To see tests, see here: http://jsfiddle.net/wRufK/. Yes I know this is in JavaScript and not C#, but jsfiddle is a very convenient way to show code in action. There are differences though -- in C# we use
Regex.matchand the JavaScript regex has extra backslashes to escape the inner forward slashes.indexOfmight be overkill depending on the application. If you want to find all matches, see http://msdn.microsoft.com/en-us/library/twcw2f1c.aspx for info on repeated matching. You can also modify the regexes for capturing.Since your dates can be in any of the forms above, and probably others, a single regex might be preferable. A very flexible date finder is here: http://www.regular-expressions.info/dates.html. You might want to consider it instead of fixing an exact set.