如何在 C++ 中解析和验证 std::string 中的日期？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/19482378/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How to parse and validate a date in std::string in C++?
提问by emufossum13
I'm working on a project where I have to read a date to make sure that it's a valid date. For example, February 29th is only a valid date on leap years, or June 31st is not a valid date, so the computer would output that information based on the input. My issue is that I can't figure out how to parse the string so that the user can enter "05/11/1996" as a date (for example) and then take that and put it into seperate integers. I was thinking about trying to do something with a while loop and string stream, but I'm a little stuck. If someone could help me with this, I would really appreciate it.
我正在做一个项目，我必须阅读一个日期以确保它是一个有效的日期。例如，2 月 29 日只是闰年的有效日期，或者 6 月 31 日不是有效日期，因此计算机将根据输入输出该信息。我的问题是我无法弄清楚如何解析字符串以便用户可以输入“05/11/1996”作为日期（例如），然后将其放入单独的整数中。我正在考虑尝试用 while 循环和字符串流做一些事情，但我有点卡住了。如果有人能帮助我解决这个问题，我将不胜感激。
采纳答案by DrM
If the format is like in your example, you could take out the integer like this:
如果格式类似于您的示例，您可以像这样取出整数：
int day, month, year;
sscanf(buffer, "%2d/%2d/%4d",
&month,
&day,
&year);
where of course in buffer you have the date ("05/11/1996" )
当然在缓冲区中你有日期（“05/11/1996”）
回答by LihO
A possible solution might be also based on strptime, however note that this function only validates whether the day is from the interval <1;31>and month from <1;12>, i.e. "30/02/2013"is valid still:
一个可能的解决方案也可能基于strptime，但请注意，此函数仅验证日期是否来自 间隔<1;31>和月份<1;12>，即"30/02/2013"仍然有效：
#include <iostream>
#include <ctime>
int main() {
struct tm tm;
std::string s("32/02/2013");
if (strptime(s.c_str(), "%d/%m/%Y", &tm))
std::cout << "date is valid" << std::endl;
else
std::cout << "date is invalid" << std::endl;
}
strptimestrptime并非总是可用并且额外的验证会很好，因此您可以执行以下操作：
- extract day, month, year
- fill
struct tm - normalize it
- check whether normalized date is still the same as retrieved day, month, year
- 提取日、月、年
- 填
struct tm - 正常化
- 检查标准化日期是否仍与检索到的日、月、年相同
i.e.:
IE：
#include <iostream>
#include <sstream>
#include <ctime>
// function expects the string in format dd/mm/yyyy:
bool extractDate(const std::string& s, int& d, int& m, int& y){
std::istringstream is(s);
char delimiter;
if (is >> d >> delimiter >> m >> delimiter >> y) {
struct tm t = {0};
t.tm_mday = d;
t.tm_mon = m - 1;
t.tm_year = y - 1900;
t.tm_isdst = -1;
// normalize:
time_t when = mktime(&t);
const struct tm *norm = localtime(&when);
// the actual date would be:
// m = norm->tm_mon + 1;
// d = norm->tm_mday;
// y = norm->tm_year;
// e.g. 29/02/2013 would become 01/03/2013
// validate (is the normalized date still the same?):
return (norm->tm_mday == d &&
norm->tm_mon == m - 1 &&
norm->tm_year == y - 1900);
}
return false;
}
used as:
用作：
int main() {
std::string s("29/02/2013");
int d,m,y;
if (extractDate(s, d, m, y))
std::cout << "date "
<< d << "/" << m << "/" << y
<< " is valid" << std::endl;
else
std::cout << "date is invalid" << std::endl;
}
which in this case would output date is invalidsince normalization would detect that 29/02/2013has been normalized to 01/03/2013.
在这种情况下将输出，date is invalid因为标准化会检测到29/02/2013已标准化为01/03/2013.
回答by Joe
回答by sehe
I'd prefer to use Boost DateTime:
我更喜欢使用 Boost DateTime：
See it Live on Coliru
看到它住在Coliru
#include <iostream>
#include <boost/date_time/local_time/local_time.hpp>
struct dateparser
{
dateparser(std::string fmt)
{
// set format
using namespace boost::local_time;
local_time_input_facet* input_facet = new local_time_input_facet();
input_facet->format(fmt.c_str());
ss.imbue(std::locale(ss.getloc(), input_facet));
}
bool operator()(std::string const& text)
{
ss.clear();
ss.str(text);
bool ok = ss >> pt;
if (ok)
{
auto tm = to_tm(pt);
year = tm.tm_year;
month = tm.tm_mon + 1; // for 1-based (1:jan, .. 12:dec)
day = tm.tm_mday;
}
return ok;
}
boost::posix_time::ptime pt;
unsigned year, month, day;
private:
std::stringstream ss;
};
int main(){
dateparser parser("%d/%m/%Y"); // not thread safe
// parse
for (auto&& txt : { "05/11/1996", "30/02/1983", "29/02/2000", "29/02/2001" })
{
if (parser(txt))
std::cout << txt << " -> " << parser.pt << " is the "
<< parser.day << "th of "
<< std::setw(2) << std::setfill('0') << parser.month
<< " in the year " << parser.year << "\n";
else
std::cout << txt << " is not a valid date\n";
}
}
Outputs:
输出：
05/11/1996 -> 1996-Nov-05 00:00:00 is the 5th of 11 in the year 96
30/02/1983 is not a valid date
29/02/2000 -> 2000-Feb-29 00:00:00 is the 29th of 02 in the year 100
29/02/2001 is not a valid date
