1Class::Loader(3) User Contributed Perl Documentation Class::Loader(3)
2
6 Class::Loader - Load modules and create objects on demand.
7
9 $Revision: 2.2 $
10 $Date: 2001/07/18 20:21:39 $
11
13 package Web::Server;
14 use Class::Loader;
15 @ISA = qw(Class::Loader);
16 $self->_load( 'Content_Handler', {
18 Module => "Filter::URL",
19 Constructor => "new",
20 Args => [ ],
21 }
22 );
23
25 Certain applications like to defer the decision to use a particular
26 module till runtime. This is possible in perl, and is a useful trick in
27 situations where the type of data is not known at compile time and the
28 application doesn't wish to pre-compile modules to handle all types of
29 data it can work with. Loading modules at runtime can also provide
30 flexible interfaces for perl modules. Modules can let the programmer
31 decide what modules will be used by it instead of hard-coding their
32 names.
33 Class::Loader is an inheritable class that provides a method, _load(),
35 to load a module from disk and construct an object by calling its con‐
36 structor. It also provides a way to map modules names and associated
37 metadata with symbolic names that can be used in place of module names
38 at _load().
39
41 new()
42 A basic constructor. You can use this to create an object of
43 Class::Loader, in case you don't want to inherit Class::Loader.
44 _load()
46 _load() loads a module and calls its constructor. It returns the
47 newly constructed object on success or a non-true value on failure.
48 The first argument can be the name of the key in which the returned
49 object is stored. This argument is optional. The second (or the
50 first) argument is a hash which can take the following keys:
51 Module
53 This is name of the class to load. (It is not the module's
54 filename.)
55 Name
57 Symbolic name of the module defined with _storemap(). Either
58 one of Module or Name keys must be present in a call to
59 _load().
60 Constructor
62 Name of the Module constructor. Defaults to "new".
63 Args
65 A reference to the list of arguments for the constructor.
66 _load() calls the constructor with this list. If no Args are
67 present, _load() will call the constructor without any argu‐
68 ments.
69 CPAN
71 If the Module is not installed on the local system, _load() can
72 fetch & install it from CPAN provided the CPAN key is present.
73 This functionality assumes availability of a pre-configured
74 CPAN shell.
75 _storemap()
77 Class::Loader maintains a class table that maps symbolic names to
78 parameters accepted by _load(). It takes a hash as argument whose
79 keys are symbolic names and value are hash references that contain
80 a set of _load() arguments. Here's an example:
81 $self->_storemap ( "URL" => { Module => "Filter::URL",
83 Constructor => "foo",
84 Args => [qw(bar baz)],
85 }
86 );
87 # time passes...
89 $self->{handler} = $self->_load ( Name => 'URL' );
91 _retrmap()
93 _retrmap() returns the entire map stored with Class::Loader.
94 Class::Loader maintains separate maps for different classes, and
95 _retrmap() returns the map valid in the caller class.
96
98 AnyLoader(3)
99
101 Vipul Ved Prakash, <mail@vipul.net>
102
104 Copyright (c) 2001, Vipul Ved Prakash. All rights reserved. This code
105 is free software; you can redistribute it and/or modify it under the
106 same terms as Perl itself.
107perl v5.8.8 2007-04-18 Class::Loader(3)