Dear list,
A pattern seen frequently in DateTime::Calendar-like modules is to put the
functionality in a top-level module which holds a DateTime object to do the
DateTime-specific stuff. If you want anything like the full DateTime
functionality this involves writing a bunch of methods on the order of
sub some_method { $_[0]->{dt}->some_method( @_[ 1 .. $#_ ] ) }
Fortunately if I turn off strict refs the methods can be defined in a loop by
assigning an anonymous subroutine to a glob. But the above is not the only
subroutine template, merely the most common.
It seems to me that in at least some such cases subclassing DateTime would be a
better alternative. But I find no documentation on how to do this. I made a
sort of middle-level pass through http://datetime.perl.org/, and browsed the
mailing list archives back to 2012 or so. Did I miss the documentation somehow?
If so, could someone give me a pointer to it?
The main issue I see are:
* Where can I, in some supported way, stash any extra attribute values?
* Is there a naming convention to avoid method name conflicts (i.e.
unintentional overrides), especially for private methods?
You can stop reading here unless you are curious about what motivated the
question. Feel free to snip it in a reply.
My reason for asking is that I have adopted a couple modules that use this
pattern: DateTime::Calendar::Christian and
DateTime::Fiction::JRRTolkien::Shire. Both were missing some DateTime
functionality of interest to me -- a lot in the latter case. A bunch of methods
had to be written to get it, and these methods have a strong family resemblance.
When I was going through the process of adopting DateTime::Calendar::Christian
I was offered DateTime::Calendar::Liturgical::Christian. I refused, because I
do not have the religious background to understand the first thing about what
feast we celebrate today or what color altar cloth to use;
DateTIme::Calendar::Christian just does the Julian calendar before the
conversion date and the Gregorian calendar after.
Well, I decided to take another look at
DateTime::Calendar::Liturgical::Christian, found myself writing those same
methods for a second or third time, and decided maybe some laziness was in
order. I started writing a class that does not inherit from DateTime but uses
the $self->{dt} pattern, AND that passes all the DateTime tests. This is mostly
just drudgery, but the methods that take two DateTime arguments (e.g.
subtract_datetime()) are turning out to be problematic. So I thought,
belatedly, that I would look into doing the simple obvious thing rather than
the complex obscure thing.
Thanks,
Tom Wyant
