use warnings;
use Scalar::Util 'blessed';
+use Algorithm::C3;
-our $VERSION = '0.10';
+our $VERSION = '0.11';
# this is our global stash of both
# MRO's and method dispatch tables
## initializers
-# NOTE:
-# this will not run under the following
-# conditions:
-# - mod_perl
-# - require Class::C3;
-# - eval "use Class::C3"
-# in all those cases, you need to call
-# the initialize() function manually
-INIT { initialize() }
-
sub initialize {
# why bother if we don't have anything ...
return unless keys %MRO;
## functions for calculating C3 MRO
-# this function is a perl-port of the
-# python code on this page:
-# http://www.python.org/2.3/mro.html
-sub _merge {
- my (@seqs) = @_;
- my $class_being_merged = $seqs[0]->[0];
- my @res;
- while (1) {
- # remove all empty seqences
- my @nonemptyseqs = (map { (@{$_} ? $_ : ()) } @seqs);
- # return the list if we have no more no-empty sequences
- return @res if not @nonemptyseqs;
- my $reject;
- my $cand; # a canidate ..
- foreach my $seq (@nonemptyseqs) {
- $cand = $seq->[0]; # get the head of the list
- my $nothead;
- foreach my $sub_seq (@nonemptyseqs) {
- # XXX - this is instead of the python "in"
- my %in_tail = (map { $_ => 1 } @{$sub_seq}[ 1 .. $#{$sub_seq} ]);
- # NOTE:
- # jump out as soon as we find one matching
- # there is no reason not too. However, if
- # we find one, then just remove the '&& last'
- ++$nothead && last if exists $in_tail{$cand};
- }
- last unless $nothead; # leave the loop with our canidate ...
- $reject = $cand;
- $cand = undef; # otherwise, reject it ...
- }
- die "Inconsistent hierarchy found while merging '$class_being_merged':\n\t" .
- "current merge results [\n\t\t" . (join ",\n\t\t" => @res) . "\n\t]\n\t" .
- "mergeing failed on '$reject'\n" if not $cand;
- push @res => $cand;
- # now loop through our non-empties and pop
- # off the head if it matches our canidate
- foreach my $seq (@nonemptyseqs) {
- shift @{$seq} if $seq->[0] eq $cand;
- }
- }
-}
-
sub calculateMRO {
my ($class) = @_;
- no strict 'refs';
- return _merge(
- [ $class ], # the class we are linearizing
- (map { [ calculateMRO($_) ] } @{"${class}::ISA"}), # the MRO of all the superclasses
- [ @{"${class}::ISA"} ] # a list of all the superclasses
- );
+ return Algorithm::C3::merge($class, sub {
+ no strict 'refs';
+ @{$_[0] . '::ISA'};
+ });
}
package # hide me from PAUSE
# <D>
package main;
+
+ # initializez the C3 module
+ # (formerly called in INIT)
+ Class::C3::initialize();
print join ', ' => Class::C3::calculateMRO('Diamond_D') # prints D, B, C, A
=head1 DESCRIPTION
-This is currently an experimental pragma to change Perl 5's standard method resolution order
-from depth-first left-to-right (a.k.a - pre-order) to the more sophisticated C3 method resolution
-order.
+This is pragma to change Perl 5's standard method resolution order from depth-first left-to-right
+(a.k.a - pre-order) to the more sophisticated C3 method resolution order.
=head2 What is C3?
=head2 How does this module work?
-This module uses a technique similar to Perl 5's method caching. During the INIT phase, this module
-calculates the MRO of all the classes which called C<use Class::C3>. It then gathers information from
-the symbol tables of each of those classes, and builds a set of method aliases for the correct
-dispatch ordering. Once all these C3-based method tables are created, it then adds the method aliases
-into the local classes symbol table.
+This module uses a technique similar to Perl 5's method caching. When C<Class::C3::initialize> is
+called, this module calculates the MRO of all the classes which called C<use Class::C3>. It then
+gathers information from the symbol tables of each of those classes, and builds a set of method
+aliases for the correct dispatch ordering. Once all these C3-based method tables are created, it
+then adds the method aliases into the local classes symbol table.
The end result is actually classes with pre-cached method dispatch. However, this caching does not
do well if you start changing your C<@ISA> or messing with class symbol tables, so you should consider
=item B<initialize>
-This can be used to initalize the C3 method dispatch tables. You need to call this if you are running
-under mod_perl, or in any other environment which does not run the INIT phase of the perl compiler.
+This B<must be called> to initalize the C3 method dispatch tables, this module B<will not work> if
+you do not do this. It is advised to do this as soon as possible B<after> any classes which use C3.
+
+This function used to be called automatically for you in the INIT phase of the perl compiler, but
+that lead to warnings if this module was required at runtime. After discussion with my user base
+(the L<DBIx::Class> folks), we decided that calling this in INIT was more of an annoyance than a
+convience. I apologize to anyone this causes problems for (although i would very suprised if I had
+any other users other than the L<DBIx::Class> folks). The simplest solution of course is to define
+your own INIT method which calls this function.
NOTE:
This can B<not> be used to re-load the dispatch tables for all classes. Use C<reinitialize> for that.
The next thing to keep in mind is that you will need to pass all arguments to C<next::method> it can
not automatically use the current C<@_>.
-=head1 CAVEATS
+There are some caveats about using C<next::method>, see below for those.
-Let me first say, this is an experimental module, and so it should not be used for anything other
-then other experimentation for the time being.
+=head1 CAVEATS
-That said, it is the authors intention to make this into a completely usable and production stable
-module if possible. Time will tell.
+This module used to be labeled as I<experimental>, however it has now been pretty heavily tested by
+the good folks over at L<DBIx::Class> and I am confident this module is perfectly usable for
+whatever your needs might be.
-And now, onto the caveats.
+But there are still caveats, so here goes ...
=over 4
=item Adding/deleting methods from class symbol tables.
-This module calculates the MRO for each requested class during the INIT phase by interogatting the symbol
-tables of said classes. So any symbol table manipulation which takes place after our INIT phase is run will
-not be reflected in the calculated MRO. Just as with changing the C<@ISA>, you will need to call
-C<reinitialize> for any changes you make to take effect.
+This module calculates the MRO for each requested class by interogatting the symbol tables of said classes.
+So any symbol table manipulation which takes place after our INIT phase is run will not be reflected in
+the calculated MRO. Just as with changing the C<@ISA>, you will need to call C<reinitialize> for any
+changes you make to take effect.
-=back
+=item Calling C<next::method> from methods defined outside the class
-=head1 TODO
+There is an edge case when using C<next::method> from within a subroutine which was created in a different
+module than the one it is called from. It sounds complicated, but it really isn't. Here is an example which
+will not work correctly:
-=over 4
+ *Foo::foo = sub { (shift)->next::method(@_) };
+
+The problem exists because the anonymous subroutine being assigned to the glob C<*Foo::foo> will show up
+in the call stack as being called C<__ANON__> and not C<foo> as you might expect. Since C<next::method>
+uses C<caller> to find the name of the method it was called in, it will fail in this case.
-=item More tests
+But fear not, there is a simple solution. The module C<Sub::Name> will reach into the perl internals and
+assign a name to an anonymous subroutine for you. Simply do this:
+
+ use Sub::Name 'subname';
+ *Foo::foo = subname 'Foo::foo' => sub { (shift)->next::method(@_) };
-You can never have enough tests :)
+and things will Just Work. Of course this is not always possible to do, but to be honest, I just can't
+manage to find a workaround for it, so until someone gives me a working patch this will be a known
+limitation of this module.
=back
projects / gitmo/Class-C3.git / commitdiff