Re: [Boost-users] [date time] using date_facet to output to a stream once

Subject: Re: [Boost-users] [date time] using date_facet to output to a stream once
From: Steve Lorimer (steve.lorimer_at_[hidden])
Date: 2010-06-15 10:26:38

I have made some progress, but am now getting unexpected results:

I have the following in my class:

    date_facet* fmt;
    mutable std::stringstream desig_stream;

and I do the following in my constructor:

    fmt(new date_facet);
    desig_stream.imbue(std::locale(std::locale::classic(), fmt));

at some point in my code I call

    fmt->format("%b %y"); // Mmm yy

and in my class's operator<<(ostream&...) I do the following:

    e.desig_stream.str("");
    e.desig_stream << e.desig;
    os << e.desig_stream.str();

because of the fact that I set the format to "%b %y", I would expect to see
"*Dec 1**0*", instead, I'm getting "*2010-Dec-01 00:00:00*"

What must I change for my stringstream / date_facet objects to work together
such that I can output a ptime object to a stream and obtain the expected
format "*%b %y*"?

TIA
Steve

On 15 June 2010 14:38, Steve Lorimer <steve.lorimer_at_[hidden]> wrote:

> Hi
>
> I have a an object which contains a ptime and an int mask. The mask tells
> me that regardless of the value stored inside the ptime object, I should
> display the ptime as such.
>
> If you look at the code below (set_fmt function), I set the format of a
> date_facet object according to some bitmasks.
>
> I now want to use this date_facet together with my ptime to output the
> ptime value to an outputstream?
> I don't want it to change the outputstream's settings for ALL ptime values,
> just for this single instance
>
> All the examples use a date_facet allocated on the heap, and use
> std::cout.imbue(...), whereas I'm looking for functionality similar to
> strftime... is this possible?
>
> eg:
>
> class expiration
> {
>     enum expiry_mask
>     {
>         expiry_null   = 0x00,
>         expiry_year   = 0x01,
>         expiry_month  = 0x02,
>         expiry_day    = 0x04,
>         expiry_hour   = 0x08,
>         expiry_minute = 0x10,
>         expiry_second = 0x20,
>         expiry_date   = 0x07, // yyyy/mm/dd
>         expiry_time   = 0x38, // hh:nn:ss
>         expiry_all    = 0x3f  // yyyy/mm/dd hh:nn:ss
>     };
>
> boost::posix_time::ptime desig;
> int32_t desig_mask;
> boost::gregorian::date_facet fmt;
>
>
> public:
>
> void expiration::set_fmt(const int32_t mask)
> {
>     switch(mask & expiry_date) *// strip off time part of mask*
>     {
>         case expiry_null:
>             fmt.format("");
>             break;
>         case expiry_year | expiry_month | expiry_day: *// display as "**dd
> Mmm yy"*
>             fmt.format("%d %b %y");
>             break;
>         case expiry_year | expiry_month: *// display as **"Mmm yy"*
>             fmt.format("%b %y");
>             break;
>         case expiry_year: *// display as "**yy"*
>             fmt.format("%y");
>             break;
>         default:
>             break;
>     }
> }
>
> ... some other stuff here ...
>
>
> };
>
> Thanks
> Steve
>