1Class::Load(3)        User Contributed Perl Documentation       Class::Load(3)
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NAME

6       Class::Load - a working (require "Class::Name") and more
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VERSION

9       version 0.20
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SYNOPSIS

12           use Class::Load ':all';
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14           try_load_class('Class::Name')
15               or plan skip_all => "Class::Name required to run these tests";
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17           load_class('Class::Name');
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19           is_class_loaded('Class::Name');
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21           my $baseclass = load_optional_class('Class::Name::MightExist')
22               ? 'Class::Name::MightExist'
23               : 'Class::Name::Default';
24

DESCRIPTION

26       "require EXPR" only accepts "Class/Name.pm" style module names, not
27       "Class::Name". How frustrating! For that, we provide "load_class
28       'Class::Name'".
29
30       It's often useful to test whether a module can be loaded, instead of
31       throwing an error when it's not available. For that, we provide
32       "try_load_class 'Class::Name'".
33
34       Finally, sometimes we need to know whether a particular class has been
35       loaded.  Asking %INC is an option, but that will miss inner packages
36       and any class for which the filename does not correspond to the package
37       name. For that, we provide "is_class_loaded 'Class::Name'".
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FUNCTIONS

40   load_class Class::Name, \%options
41       "load_class" will load "Class::Name" or throw an error, much like
42       "require".
43
44       If "Class::Name" is already loaded (checked with "is_class_loaded")
45       then it will not try to load the class. This is useful when you have
46       inner packages which "require" does not check.
47
48       The %options hash currently accepts one key, "-version". If you specify
49       a version, then this subroutine will call "Class::Name->VERSION(
50       $options{-version} )" internally, which will throw an error if the
51       class's version is not equal to or greater than the version you
52       requested.
53
54       This method will return the name of the class on success.
55
56   try_load_class Class::Name, \%options -> (0|1, error message)
57       Returns 1 if the class was loaded, 0 if it was not. If the class was
58       not loaded, the error will be returned as a second return value in list
59       context.
60
61       Again, if "Class::Name" is already loaded (checked with
62       "is_class_loaded") then it will not try to load the class. This is
63       useful when you have inner packages which "require" does not check.
64
65       Like "load_class", you can pass a "-version" in %options. If the
66       version is not sufficient, then this subroutine will return false.
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68   is_class_loaded Class::Name, \%options -> 0|1
69       This uses a number of heuristics to determine if the class
70       "Class::Name" is loaded. There heuristics were taken from Class::MOP's
71       old pure-perl implementation.
72
73       Like "load_class", you can pass a "-version" in %options. If the
74       version is not sufficient, then this subroutine will return false.
75
76   load_first_existing_class Class::Name, \%options, ...
77       This attempts to load the first loadable class in the list of classes
78       given. Each class name can be followed by an options hash reference.
79
80       If any one of the classes loads and passes the optional version check,
81       that class name will be returned. If none of the classes can be loaded
82       (or none pass their version check), then an error will be thrown.
83
84       If, when attempting to load a class, it fails to load because of a
85       syntax error, then an error will be thrown immediately.
86
87   load_optional_class Class::Name, \%options -> 0|1
88       "load_optional_class" is a lot like "try_load_class", but also a lot
89       like "load_class".
90
91       If the class exists, and it works, then it will return 1. If you
92       specify a version in %options, then the version check must succeed or
93       it will return 0.
94
95       If the class doesn't exist, and it appears to not exist on disk either,
96       it will return 0.
97
98       If the class exists on disk, but loading from disk results in an error
99       ( i.e.: a syntax error ), then it will "croak" with that error.
100
101       This is useful for using if you want a fallback module system, i.e.:
102
103           my $class = load_optional_class($foo) ? $foo : $default;
104
105       That way, if $foo does exist, but can't be loaded due to error, you
106       won't get the behaviour of it simply not existing.
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SEE ALSO

109       <http://blog.fox.geek.nz/2010/11/searching-design-spec-for-ultimate.html>
110           This blog post is a good overview of the current state of the
111           existing modules for loading other modules in various ways.
112
113       <http://blog.fox.geek.nz/2010/11/handling-optional-requirements-with.html>
114           This blog post describes how to handle optional modules with
115           Class::Load.
116
117       <http://d.hatena.ne.jp/tokuhirom/20110202/1296598578>
118           This Japanese blog post describes why DBIx::Skinny now uses
119           Class::Load over its competitors.
120
121       Moose, Jifty, Prophet, etc
122           This module was designed to be used anywhere you have "if (eval
123           "require $module"; 1)", which occurs in many large projects.
124

AUTHOR

126       Shawn M Moore <sartak at bestpractical.com>
127

129       This software is copyright (c) 2012 by Shawn M Moore.
130
131       This is free software; you can redistribute it and/or modify it under
132       the same terms as the Perl 5 programming language system itself.
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136perl v5.16.3                      2012-07-15                    Class::Load(3)
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