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(jeffa) Re: Runtime instantiation decisions

by jeffa (Chancellor)
on Mar 30, 2002 at 17:01 UTC ( #155442=note: print w/ replies, xml ) Need Help??


in reply to Runtime instantiation decisions

Ahhh, the Factory Pattern!

All you need to do is make Astro::Observation the factory. It will return a class depending on what argument it receives. Here is a simple way to implement Astro::Observation:

package Astro::Observation; use Astro::Observation::Simple; use Astro::Observation::Complex; sub new { my $self = shift; my $class = shift; return Astro::Observation::Simple->new(@_) if 'simple' eq $class; return Astro::Observation::Complex->new(@_) if 'complex' eq $class; return undef; }
Which can be called like so:
my $obs = Astro::Observation->new("simple",'foo'); my $obc = Astro::Observation->new("complex",'bar');
But this way gets tiresome after you add more classes that the factory can deliver. I am quite sure that this can be avoided by using eval somehow.

UPDATE: once again - just do what the wise and resourceful Kanji said.

UPDATE x 2: that's what i was trying to do! :D
Here is a tar ball should anyone want to try this out.

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)


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