LanX has asked for the wisdom of the Perl Monks concerning the following question:
Lets say we have two classes Container and Element
and you can
- add Elements to a Container
- extract them
- apply method chaining
my $cont = Container->new(); my $elem = Element->new('name'); $cont->add_elem($elem); # method chaining $cont1->get_elem('name')->do_something(); # identical to $elem1 = $cont1->get_elem('name'); $elem1->do_something(); # *
For this to work does $elem2 obviously need to know that it belongs to $container.
So it's N->1 : N Element -> 1 Container
and $elem1 == $elem
with updated property $elem->{member_of}=$cont Now after using this for a long time new requirements arise and Elements need to belong to multiple Containers.
So now it's N->M : N Element -> M Container
Clearly the old model with $elem2 == $elem doesn't work anymore because
$elem2 = $cont2->get_elem('name'); can't be member_of two different containers to allow method chaining
I don't think that $elem1 and $elem2 should belong to class Element either, but to a "wrapper" class ContainerElement referencing $elem, i.e. $elem1->{master}=$elem
Then I could think of many solutions, some involving inheritance, some AUTOLOAD to make sure that
$elem1->do_something(...) always does $elem1->{master}->do_something(..)
without hardcoding all methods.
I don't wanna reinvent the wheel and I'm already starting to worry too much about performance so here the question ...
What are the usual OO-Patterns to solve this? :)
Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery
update
*) OK Sorry, do_something() is doing something with the relation $cont <- $elem like set_weight($cont,$elem)