1N/A# Time-stamp: "2000-05-13 20:03:22 MDT" -*-Perl-*- 1N/AClass::ISA -- report the search path for a class's ISA tree 1N/A # Suppose you go: use Food::Fishstick, and that uses and 1N/A # inherits from other things, which in turn use and inherit 1N/A # from other things. And suppose, for sake of brevity of 1N/A # example, that their ISA tree is the same as: 1N/A @Food::Fishstick::ISA = qw(Food::Fish Life::Fungus Chemicals); 1N/A @Food::Fish::ISA = qw(Food); 1N/A @Food::ISA = qw(Matter); 1N/A @Life::Fungus::ISA = qw(Life); 1N/A @Chemicals::ISA = qw(Matter); 1N/A @Life::ISA = qw(Matter); 1N/A @Matter::ISA = qw(); 1N/A print "Food::Fishstick path is:\n ", 1N/A join(", ", Class::ISA::super_path('Food::Fishstick')), 1N/A Food::Fishstick path is: 1N/A Food::Fish, Food, Matter, Life::Fungus, Life, Chemicals 1N/ASuppose you have a class (like Food::Fish::Fishstick) that is derived, 1N/Avia its @ISA, from one or more superclasses (as Food::Fish::Fishstick 1N/Ais from Food::Fish, Life::Fungus, and Chemicals), and some of those 1N/Asuperclasses may themselves each be derived, via its @ISA, from one or 1N/Amore superclasses (as above). 1N/AWhen, then, you call a method in that class ($fishstick->calories), 1N/APerl first searches there for that method, but if it's not there, it 1N/Agoes searching in its superclasses, and so on, in a depth-first (or 1N/Amaybe "height-first" is the word) search. In the above example, it'd 1N/Afirst look in Food::Fish, then Food, then Matter, then Life::Fungus, 1N/Athen Life, then Chemicals. 1N/AThis library, Class::ISA, provides functions that return that list -- 1N/Athe list (in order) of names of classes Perl would search to find a 1N/Amethod, with no duplicates. 1N/A=item the function Class::ISA::super_path($CLASS) 1N/AThis returns the ordered list of names of classes that Perl would 1N/Asearch thru in order to find a method, with no duplicates in the list. 1N/A$CLASS is not included in the list. UNIVERSAL is not included -- if 1N/Ayou need to consider it, add it to the end. 1N/A=item the function Class::ISA::self_and_super_path($CLASS) 1N/AJust like C<super_path>, except that $CLASS is included as the first 1N/A=item the function Class::ISA::self_and_super_versions($CLASS) 1N/AThis returns a hash whose keys are $CLASS and its 1N/A(super-)superclasses, and whose values are the contents of each 1N/Aclass's $VERSION (or undef, for classes with no $VERSION). 1N/AThe code for self_and_super_versions is meant to serve as an example 1N/Afor precisely the kind of tasks I anticipate that self_and_super_path 1N/Aand super_path will be used for. You are strongly advised to read the 1N/Asource for self_and_super_versions, and the comments there. 1N/A=head1 CAUTIONARY NOTES 1N/A* Class::ISA doesn't export anything. You have to address the 1N/Afunctions with a "Class::ISA::" on the front. 1N/A* Contrary to its name, Class::ISA isn't a class; it's just a package. 1N/A* Say you have a loop in the ISA tree of the class you're calling one 1N/Aof the Class::ISA functions on: say that Food inherits from Matter, 1N/Abut Matter inherits from Food (for sake of argument). If Perl, while 1N/Asearching for a method, actually discovers this cyclicity, it will 1N/Athrow a fatal error. The functions in Class::ISA effectively ignore 1N/Athis cyclicity; the Class::ISA algorithm is "never go down the same 1N/Apath twice", and cyclicities are just a special case of that. 1N/A* The Class::ISA functions just look at @ISAs. But theoretically, I 1N/Asuppose, AUTOLOADs could bypass Perl's ISA-based search mechanism and 1N/Ado whatever they please. That would be bad behavior, tho; and I try 1N/Anot to think about that. 1N/A* If Perl can't find a method anywhere in the ISA tree, it then looks 1N/Ain the magical class UNIVERSAL. This is rarely relevant to the tasks 1N/Athat I expect Class::ISA functions to be put to, but if it matters to 1N/Ayou, then instead of this: 1N/A @supers = Class::Tree::super_path($class); 1N/A @supers = (Class::Tree::super_path($class), 'UNIVERSAL'); 1N/AAnd don't say no-one ever told ya! 1N/A* When you call them, the Class::ISA functions look at @ISAs anew -- 1N/Athat is, there is no memoization, and so if ISAs change during 1N/Aruntime, you get the current ISA tree's path, not anything memoized. 1N/AHowever, changing ISAs at runtime is probably a sign that you're out 1N/ACopyright (c) 1999, 2000 Sean M. Burke. All rights reserved. 1N/AThis library is free software; you can redistribute it and/or modify 1N/Ait under the same terms as Perl itself. 1N/ASean M. Burke C<sburke@cpan.org> 1N/A########################################################################### 1N/A $_ => (
defined(${
"$_\::VERSION"}) ? ${
"$_\::VERSION"} :
undef)
1N/A# Also consider magic like: 1N/A# my %class2SomeHashr = 1N/A# map { defined(%{"$_\::SomeHash"}) ? ($_ => \%{"$_\::SomeHash"}) : () } 1N/A# Class::ISA::self_and_super_path($class); 1N/A# to get a hash of refs to all the defined (and non-empty) hashes in 1N/A# $class and its superclasses. 1N/A# Or even consider this incantation for doing something like hash-data 1N/A# map { defined(%{"$_\::SomeHash"}) ? %{"$_\::SomeHash"}) : () } 1N/A# reverse(Class::ISA::self_and_super_path($class)); 1N/A# Consider that reverse() is necessary because with 1N/A# %foo = ('a', 'wun', 'b', 'tiw', 'a', 'foist'); 1N/A# $foo{'a'} is 'foist', not 'wun'. 1N/A########################################################################### 1N/A#-------------------------------------------------------------------------- 1N/A # Assumption: searching is depth-first. 1N/A # Assumption: '' (empty string) can't be a class package name. 1N/A # Note: 'UNIVERSAL' is not given any special treatment. 1N/A return ()
unless @_;
1N/A {
my $c = $_;
# copy, to avoid being destructive 1N/A substr($c,
0,
2) =
"main::" if substr($c,
0,
2)
eq '::';
1N/A # Canonize the :: -> main::, ::foo -> main::foo thing. 1N/A # Should I ever canonize the Foo'Bar = Foo::Bar thing? 1N/A # I.e., if this class has any parents (at least, ones I've never seen 1N/A # before), push them, in order, onto the stack of classes I need to 1N/A#--------------------------------------------------------------------------