First some definitions:
- Factory
- A class that generates instances of other classes, choosing which class to
build on the basis of run-time information.
- Façade
- A class that acts as a front-end for one or more other classes, delegating
the actual work to those classes as appropriate.
In your particular example, what you want is a factory: a class that
generates objects according to where the sun rises. For example:
# Rational helper class...
package Astro::Data::Scientific;
use base Solar::Data;
use base Lunar::Data;
# <define methods here>
# "Differently rational" helper class...
package Astro::Data::Mythological;
use base Astrological::Data; # Pre-empt normal methods
use base Astro::Data::Scientific;
# <overload any methods here that the
# heavens dictate should behave differently>
# Factory class...
package Astro::Data;
# Constructor returns instances of helper classes,
# depending on run-time astro[nl]o[mg]ical conditions
sub new {
shift; # off class name
if ($sun_rises_in_west) {
return Astro::Data::Mythological->new(@_);
}
else {
return Astro::Data::Scientific->new(@_);
}
}
# <no methods of its own, since it's never actually instantiated>
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