Convert wide character strings to boost dates

Answer 1

efotinis found a good way using from_stream .

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I've looked into the manual of date_time and found it supports facets:

#include <boost/date_time/gregorian/gregorian.hpp>
#include <iostream>
#include <sstream>
#include <locale>

int main() {
    using namespace boost::gregorian;

    std::wstringstream ss;
    wdate_input_facet * fac = new wdate_input_facet(L"%Y-%m-%d");
    ss.imbue(std::locale(std::locale::classic(), fac));

    date d;
    ss << L"2004-01-01 2005-01-01 2006-06-06";
    while(ss >> d) {
        std::cout << d << std::endl;
    }
}

You could also go with that.

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I've looked up how date facets work:

• The boost::date_time::date_input_facet template implements a facet.
• Facets are derived from std::locale::facet and every one has an unique id.
• You can imbue a new locale into a stream, replacing its old locale. The locale of a stream will be used for all sorts of parsing and conversions.
• When you create a new std::locale using the form i showed, you give it an existing locale, and a pointer to facet. The given facet will replace any existing facet of the same type in the locale given. (so, it would replace any other date_input_facet used).
• All facets are associated with the locale somehow, so that you can use std::has_facet<Facet>(some_locale) to check whether the given locale has some given facet type.
• You can use a facet from one locale by doing std::use_facet<Facet>(some_locale).some_member... .
• date_input_facet has a function get, which can be used like this:

The below is essentially done by operator>> by boost::date_type :

// assume src is a stream having the wdate_input_facet in its locale. 
// wdate_input_facet is a boost::date_time::date_input_facet<date,wchar_t> typedef.

date d;

// iterate over characters of src
std::istreambuf_iterator<wchar_t> b(src), e;

// use the facet to parse the date
std::use_facet<wdate_input_facet>(src.getloc()).get(b, e, src, d);

Answer 2

You can use the from_stream parser function:

using boost::gregorian::date;
using boost::gregorian::from_stream;

std::wstring ws( L"2008/01/01" );
date d1(from_stream(ws.begin(), ws.end()));
std::cout << d1;  // prints "2008-Jan-01"