2 MRO::Compat - mro::* interface compatibility for Perls < 5.9.5
5 package FooClass; use base qw/X Y Z/;
6 package X; use base qw/ZZZ/;
7 package Y; use base qw/ZZZ/;
8 package Z; use base qw/ZZZ/;
12 my $linear = mro::get_linear_isa('FooClass');
13 print join(q{, }, @$linear);
15 # Prints: "FooClass, X, ZZZ, Y, Z"
18 The "mro" namespace provides several utilities for dealing with method
19 resolution order and method caching in general in Perl 5.9.5 and higher.
21 This module provides those interfaces for earlier versions of Perl (back
24 It is a harmless no-op to use this module on 5.9.5+. That is to say,
25 code which properly uses MRO::Compat will work unmodified on both older
28 If you're writing a piece of software that would like to use the parts
29 of 5.9.5+'s mro:: interfaces that are supported here, and you want
30 compatibility with older Perls, this is the module for you.
32 Some parts of this code will work better and/or faster with
33 Class::C3::XS installed (which is an optional prereq of Class::C3, which
34 is in turn a prereq of this package), but it's not a requirement.
36 This module never exports any functions. All calls must be fully
37 qualified with the "mro::" prefix.
39 The interface documentation here serves only as a quick reference of
40 what the function basically does, and what differences between
41 MRO::Compat and 5.9.5+ one should look out for. The main docs in 5.9.5's
42 mro are the real interface docs, and contain a lot of other useful
46 mro::get_linear_isa($classname[, $type])
47 Returns an arrayref which is the linearized "ISA" of the given class.
48 Uses whichever MRO is currently in effect for that class by default, or
49 the given MRO (either "c3" or "dfs" if specified as $type).
51 The linearized ISA of a class is a single ordered list of all of the
52 classes that would be visited in the process of resolving a method on
53 the given class, starting with itself. It does not include any duplicate
56 Note that "UNIVERSAL" (and any members of "UNIVERSAL"'s MRO) are not
57 part of the MRO of a class, even though all classes implicitly inherit
58 methods from "UNIVERSAL" and its parents.
61 This allows the "use mro 'dfs'" and "use mro 'c3'" syntaxes, providing
62 you "use MRO::Compat" first. Please see the "USING C3" section for
65 mro::set_mro($classname, $type)
66 Sets the mro of $classname to one of the types "dfs" or "c3". Please see
67 the "USING C3" section for additional details.
69 mro::get_mro($classname)
70 Returns the MRO of the given class (either "c3" or "dfs").
72 It considers any Class::C3-using class to have C3 MRO even before
73 Class::C3::initialize() is called.
75 mro::get_isarev($classname)
76 Returns an arrayref of classes who are subclasses of the given
77 classname. In other words, classes who we exist, however indirectly, in
78 the @ISA inheritancy hierarchy of.
80 This is much slower on pre-5.9.5 Perls with MRO::Compat than it is on
81 5.9.5+, as it has to search the entire package namespace.
83 mro::is_universal($classname)
84 Returns a boolean status indicating whether or not the given classname
85 is either "UNIVERSAL" itself, or one of "UNIVERSAL"'s parents by @ISA
88 Any class for which this function returns true is "universal" in the
89 sense that all classes potentially inherit methods from it.
91 mro::invalidate_all_method_caches
92 Increments "PL_sub_generation", which invalidates method caching in all
95 Please note that this is rarely necessary, unless you are dealing with a
96 situation which is known to confuse Perl's method caching.
98 mro::method_changed_in($classname)
99 Invalidates the method cache of any classes dependent on the given
100 class. In MRO::Compat on pre-5.9.5 Perls, this is an alias for
101 "mro::invalidate_all_method_caches" above, as pre-5.9.5 Perls have no
102 other way to do this. It will still enforce the requirement that you
103 pass it a classname, for compatibility.
105 Please note that this is rarely necessary, unless you are dealing with a
106 situation which is known to confuse Perl's method caching.
108 mro::get_pkg_gen($classname)
109 Returns an integer which is incremented every time a local method of or
110 the @ISA of the given package changes on Perl 5.9.5+. On earlier Perls
111 with this MRO::Compat module, it will probably increment a lot more
112 often than necessary.
115 While this module makes the 5.9.5+ syntaxes "use mro 'c3'" and
116 "mro::set_mro("Foo", 'c3')" available on older Perls, it does so merely
117 by passing off the work to Class::C3.
119 It does not remove the need for you to call "Class::C3::initialize()",
120 "Class::C3::reinitialize()", and/or "Class::C3::uninitialize()" at the
121 appropriate times as documented in the Class::C3 docs. These three
122 functions are always provided by MRO::Compat, either via Class::C3
123 itself on older Perls, or directly as no-ops on 5.9.5+.
131 Brandon L. Black, <blblack@gmail.com>
133 COPYRIGHT AND LICENSE
134 Copyright 2007-2008 Brandon L. Black <blblack@gmail.com>
136 This library is free software; you can redistribute it and/or modify it
137 under the same terms as Perl itself.