On Tue, Dec 15, 2009 at 6:51 PM, Evan Carroll <m...@evancarroll.com> wrote:
> > Why then does parse_datetime automatically convert from a string to a
> > timezone?
> > Shouldn't it then just always return a datetime in floating context?
>
> It doesn't "convert" it "reads it as".
>
> > my $dt = $Strp->parse_datetime($my_string); #Floating
>
> Not floating, that is whatever the time_zone you have set in the
> ::Format module. Or, if the Format module reads in a different time
> zone from the string as in the case of %z and %Z in strptime.
>
I put floating for an example for not passing a time_zone parameter. Also,
I've never been able to get %Z to reliably work for parsing, just %z. And
the time_zone parameter overrides anything in your string for %z not the
other way around:
Give it a try:
my $dt = DateTime->now;
my $string1 = $dt->strftime('%m/%d/%Y %T %Z');
my $string2 = $dt->strftime('%m/%d/%Y %T %z');
print "1: $string1\n";
print "2: $string2\n";
my $Strp1 = new DateTime::Format::Strptime(
pattern => '%m/%d/%Y %T %Z',
);
my $Strp11 = new DateTime::Format::Strptime(
pattern => '%m/%d/%Y %T %Z',
time_zone => 'America/New_York',
);
my $Strp2 = new DateTime::Format::Strptime(
pattern => '%m/%d/%Y %T %z',
);
my $Strp21 = new DateTime::Format::Strptime(
pattern => '%m/%d/%Y %T %z',
time_zone => 'America/New_York',
);
my $dt1 = $Strp1->parse_datetime($string1);
my $dt11 = $Strp11->parse_datetime($string1);
my $dt2 = $Strp2->parse_datetime($string2);
my $dt21 = $Strp21->parse_datetime($string2);
print "DT 1: " . ($dt1 || "can't do it") . "\n";
print "DT 1 time_zone: " . ($dt1 || "can't do it") . "\n";
print "DT 2: " . ($dt2 || "can't do it") . "\n";
print "DT 2 time_zone: " . ($dt21 || "can't do it") . "\n";
>
> > Not overriding time_zone, just format_datetime if and only if a option is
> > set. The attribute 'time_zone' seems pretty generic to me, it's not
> > 'parse_time_zone' or 'time_zone_from_string'. The confusing part is that
> > it's just named 'time_zone'.
>
> I'm not arguing that it is the best name in the world, I'm just saying
> it is simply the respective constructor argument that well behaved
> DateTime::Format module will provide under the hood to DateTime.
>
And that part would not change.
>
> > Actually that would be pretty cool, because I could parse all of my
> DateTime
> > strings to UTC and format all my DateTime objects to a desired time_zone
> > within a single formatter.
>
> You can already do this.
>
> foreach ( qw/timezone list here/ ) {
> state $dtf = DateTime::Format::Strptime->new({ time_zone => UTC });
> my $dt = $dtf->parse_datetime( $str );
> $dt->set_time_zone( $_ );
> say "time zone $_";
> say $dtf->format_datetime( $dt );
> }
>
I agree the difference here is small, but still cool. It is also not what I
am advocating for at the moment though:
foreach ( qw/timezone list here/ ) {
state $dtf = DateTime::Format::Strptime->
>
> new({ time_zone => UTC, output_time_zone => 'America/New_York' });
> my $dt = $dtf->parse_datetime( $str );
> say "time zone $_";
> say $dtf->format_datetime( $dt );
> }
>
It would prob work more like this:
#In some master controller or sub
my $dtf = DateTime::Format::Strptime->new({ time_zone => UTC,
output_time_zone => 'America/New_York' });
#Later on form submission or input from DB
my $string_from_form_by_user = $dtf->parse_datetime($string_from_form);
#Knows the input should be converted to UTC
# LATER SOMEWHERE ELSE, possibly output to web page
my $string = $dtf->format_datetime($dt); # Knows the output should be
display based on the 'America/New_York' time_zone.
>
> > Also, why is it practical to do something like the following for parsing
> > which you appear to be fine with:
> >
> > my $Strp = new DateTime::Format::Strptime(
> > pattern => $user->datetime_pattern,
> > time_zone => 'America/New_York',
> > );
> >
> > my $Strp2 = new DateTime::Format::Strptime(
> > pattern => $user->datetime_pattern,
> > time_zone => 'America/Chicago',
> > );
>
> It is not, this is why I created DateTimeX::Format, because I wanted
> each and every DateTimeX::Format module to support a runtime override
> for the constructor arguments to DateTimeX::Format modules. So in my
> world you could just
>
> > my $Strp = new DateTimeX::Format::Strptime(
> > pattern => $user->datetime_pattern,
> > );
>
> $Strp->parse_datetime( $str, { time_zone => $tz } );
>
Nothing stopping users from:
$Strp->parse_datetime( $str, { time_zone => $tz1 } );
$Strp->parse_datetime( $str, { time_zone => $tz2 } );
>
> But the difference is I'm not really adding functionality, and nothing
> is happening under the hood to the DateTime object, just a new value
> will be supplied to the DateTime constructor.
>
I guess I still don't see how:
$Strp->format_datetime( $str, { time_zone => $tz1 } );
$Strp->format_datetime( $str, { time_zone => $tz2 } );
would be so evil. I want to get a formatted string based on pattern I
provided as it would be displayed in the specified time_zone.
>
> --
> Evan Carroll
> System Lord of the Internets
> http://www.evancarroll.com
>
