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236a4386 |
1 | package Package::Variant; |
2 | |
3 | use strictures 1; |
4 | |
5 | our %Variable; |
6 | |
7 | sub import { |
8 | my $target = caller; |
9 | my $me = shift; |
10 | my $last = (split '::', $target)[-1]; |
11 | my $anon = 'A000'; |
12 | my $variable = $target; |
13 | my %args = @_; |
14 | no strict 'refs'; |
15 | $Variable{$variable} = { |
16 | anon => $anon, |
17 | args => \%args, |
18 | subs => { |
19 | map +($_ => sub {}), @{$args{subs}||[]}, |
20 | }, |
21 | }; |
22 | *{"${target}::import"} = sub { |
23 | my $target = caller; |
0a7db8d2 |
24 | my (undef, %arg) = @_; |
25 | my $as = defined($arg{as}) ? $arg{as} : $last; |
236a4386 |
26 | no strict 'refs'; |
0a7db8d2 |
27 | *{"${target}::${as}"} = sub { |
236a4386 |
28 | $me->build_variant_of($variable, @_); |
29 | }; |
30 | }; |
31 | my $subs = $Variable{$variable}{subs}; |
32 | foreach my $name (keys %$subs) { |
33 | *{"${target}::${name}"} = sub { |
34 | goto &{$subs->{$name}} |
35 | }; |
36 | } |
37 | *{"${target}::install"} = sub { |
38 | goto &{$Variable{$variable}{install}}; |
39 | } |
40 | } |
41 | |
42 | sub build_variant_of { |
43 | my ($me, $variable, @args) = @_; |
44 | my $variant_name = "${variable}::_Variant_".++$Variable{$variable}{anon}; |
1abbe9d7 |
45 | my $import = $Variable{$variable}{args}{importing} || {}; |
46 | my $setup = join("\n", |
47 | "package ${variant_name};", |
48 | (map sprintf( |
49 | q!use %s @{$import->{'%s'}||[]};!, $_, quotemeta($_), |
50 | ), keys %$import), |
51 | "1;", |
52 | ); |
236a4386 |
53 | eval $setup |
54 | or die "evaling ${setup} failed: $@"; |
55 | my $subs = $Variable{$variable}{subs}; |
56 | local @{$subs}{keys %$subs} = map $variant_name->can($_), keys %$subs; |
57 | local $Variable{$variable}{install} = sub { |
58 | my ($name, $ref) = @_; |
59 | no strict 'refs'; |
60 | *{"${variant_name}::${name}"} = $ref; |
61 | }; |
62 | $variable->make_variant($variant_name, @args); |
63 | return $variant_name; |
64 | } |
65 | |
66 | 1; |
0c378352 |
67 | |
68 | __END__ |
69 | |
70 | =head1 NAME |
71 | |
72 | Package::Variant - Parameterizable packages |
73 | |
74 | =head1 SYNOPSIS |
75 | |
76 | # declaring a variable Moo role |
77 | package My::Role::ObjectAttr; |
78 | use strictures 1; |
79 | use Package::Variant |
80 | # what modules to 'use' |
81 | importing => { 'Moo::Role' => [] }, |
82 | # proxied subroutines |
83 | subs => [qw( has around before after extends )], |
84 | |
85 | sub make_variant { |
86 | my ($class, $target_package, %arguments) = @_; |
87 | # access arguments |
88 | my $name = $arguments{name}; |
89 | # use proxied 'has' to add an attribute |
90 | has $name => (is => 'lazy'); |
91 | # install a builder method |
92 | install "_build_${name}" => sub { |
93 | return $arguments{class}->new; |
94 | }; |
95 | } |
96 | |
97 | # using the role |
98 | package My::Class::WithObjectAttr; |
99 | use strictures 1; |
100 | use Moo; |
101 | use My::Role::ObjectAttr; |
102 | |
103 | with ObjectAttr(name => 'some_obj', class => 'Some::Class'); |
104 | |
105 | # using our class |
106 | my $obj = My::Class::WithObjectAttr->new; |
107 | $obj->some_obj; # returns a Some::Class instance |
108 | |
109 | =head1 DESCRIPTION |
110 | |
111 | This module allows you to build packages that return different variations |
112 | depending on what parameters are given. |
113 | |
114 | Users of your package will receive a subroutine able to take parameters |
115 | and return the name of a suitable variant package. The implmenetation does |
116 | not care about what kind of package it builds. |
117 | |
118 | =head2 Declaring a variable package |
119 | |
120 | There are two important parts to creating a variable package. You first |
121 | have to give C<Package::Variant> some basic information about what kind of |
122 | package you want to provide, and how. The second part is implementing a |
123 | method receiving the user's arguments and generating your variants. |
124 | |
125 | =head3 Setting up the environment for building variations |
126 | |
127 | When you C<use Package::Variant>, you pass along some arguments that |
128 | describe how you intend to build your variations. |
129 | |
130 | use Package::Variant |
131 | importing => { $package => \@import_arguments, ... }, |
132 | subs => [ @proxied_subroutine_names ]; |
133 | |
134 | The L</importing> option needs to be a hash reference with package names |
135 | to be C<use>d as keys, and array references containing the import |
136 | arguments as values. These packages will be imported into every new |
137 | variant, and need to set up every declarative subroutine you require to |
138 | build your variable package. The next option will allow you to use these |
139 | functions. |
140 | |
141 | The L</subs> option is an array reference of subroutine names that are |
142 | exported by the packages specified with L</importing>. These subroutines |
143 | will be proxied from your declaration package to the variant to be |
144 | generated. |
145 | |
146 | With L</importing> initializing your package and L</subs> declaring what |
147 | subroutines you want to use to build a variant, you can now write a |
148 | L</make_variant> method building your variants. |
149 | |
150 | =head3 Declaring a method to produce variants |
151 | |
152 | Every time a user requests a new variant a method named L</make_variant> |
153 | will be called with the name of the target package and the arguments from |
154 | the user. |
155 | |
156 | It can then use the proxied subroutines declared with L</subs> to |
157 | customize the new package. An L</install> subroutine is exported as well |
158 | allowing you to dynamically install methods into the new package. If these |
159 | options aren't flexible enough, you can use the passed name of the new |
160 | package to do any other kind of customizations. |
161 | |
162 | sub make_variant { |
163 | my ($class, $target, @arguments) = @_; |
164 | # ... |
165 | # customization goes here |
166 | # ... |
167 | } |
168 | |
169 | When the method is finished, the user will receive the name of the new |
170 | package variant you just set up. |
171 | |
172 | =head2 Using variable packages |
173 | |
174 | After your variable package is L<created|/Declaring a variable package> |
175 | your users can get a variant generating subroutine by simply importing |
176 | your package. |
177 | |
178 | use My::Variant; |
179 | my $new_variant_package = Variant( @variant_arguments ); |
180 | |
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181 | The package is now fully initialized and used. You can import the |
182 | subroutine under a different name by specifying an C<as> argument. |
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183 | |
184 | =head2 Dynamic creation of variant packages |
185 | |
186 | For regular uses, the L<normal import|/Using variable packages> provides |
187 | more than enough flexibility. However, if you want to create variations of |
188 | dynamically determined packages, you can use the L</build_variation_of> |
189 | method. |
190 | |
191 | You can use this to create variations of other packages and pass arguments |
192 | on to them to allow more modular and extensible variations. |
193 | |
194 | =head1 OPTIONS |
195 | |
196 | These are the options that can be passed when importing |
197 | C<Package::Variant>. They describe the environment in which the variants |
198 | are created. |
199 | |
200 | use Package::Variant |
201 | importing => { $package => \@import_arguments, ... }, |
202 | subs => [ @proxied_subroutines ]; |
203 | |
204 | =head2 importing |
205 | |
206 | This option is a hash reference mapping package names to array references |
207 | containing import arguments. The packages will be C<use>d with the given |
208 | arguments by every variation before the L</make_variant> method is asked |
209 | to create the package. |
210 | |
211 | =head2 subs |
212 | |
213 | An array reference of strings listing the names of subroutines that should |
214 | be proxied. These subroutines are expected to be installed into the new |
215 | variant package by the modules imported with L</importing>. Subroutines |
216 | with the same name will be availabe in your declaration package, and will |
217 | proxy through to the newly created package when used within |
218 | L</make_variant>. |
219 | |
220 | =head1 VARIABLE PACKAGE METHODS |
221 | |
222 | These are methods on the variable package you declare when you import |
223 | C<Package::Variant>. |
224 | |
225 | =head2 make_variant |
226 | |
227 | Some::Variant::Package->make_variant( $target, @arguments ); |
228 | |
229 | B<You need to provide this method.> This method will be called for every |
230 | new variant of your package. This method should use the subroutines |
231 | declared in L</subs> to customize the new variant package. |
232 | |
233 | This is a class method receiving the C<$target> package and the |
234 | C<@arguments> defining the requested variant. |
235 | |
236 | =head2 import |
237 | |
238 | use Some::Variant::Package; |
239 | my $variant_package = Package( @arguments ); |
240 | |
241 | This method is provided for you. It will allow a user to C<use> your |
242 | package and receive a subroutine taking C<@arguments> defining the variant |
243 | and returning the name of the newly created variant package. |
244 | |
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245 | The following options can be specified when importing: |
246 | |
247 | =over |
248 | |
249 | =item * B<as> |
250 | |
251 | use Some::Variant::Package as => 'Foo'; |
252 | my $variant_package = Foo( @arguments ); |
253 | |
254 | Exports the generator subroutine under a different name than the default. |
255 | |
256 | =back |
257 | |
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258 | =head1 C<Package::Variant> METHODS |
259 | |
260 | These methods are available on C<Package::Variant> itself. |
261 | |
262 | =head2 build_variation_of |
263 | |
264 | my $variant_package = Package::Variant |
265 | ->build_variation_of( $variable_package, @arguments ); |
266 | |
267 | This is the dynamic method of creating new variants. It takes the |
268 | C<$variable_package>, which is a pre-declared variable package, and a set |
269 | of C<@arguments> passed to the package to generate a new |
270 | C<$variant_package>, which will be returned. |
271 | |
272 | =head2 import |
273 | |
274 | use Package::Variant @options; |
275 | |
276 | Sets up the environment in which you declare the variants of your |
277 | packages. See L</OPTIONS> for details on the available options and |
278 | L</EXPORTS> for a list of exported subroutines. |
279 | |
280 | =head1 EXPORTS |
281 | |
282 | Additionally to the proxies for subroutines provided in L</subs>, the |
283 | following exports will be available in your variable package: |
284 | |
285 | =head2 install |
286 | |
287 | install( $method_name, $code_reference ); |
288 | |
289 | Installs a method with the given C<$method_name> into the newly created |
290 | variant package. The C<$code_reference> will be used as the body for the |
291 | method. |
292 | |
293 | =head1 AUTHOR |
294 | |
295 | =over |
296 | |
297 | =item mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk> |
298 | |
299 | =back |
300 | |
301 | =head1 COPYRIGHT |
302 | |
303 | Copyright (c) 2010-2011 the C<Package::Stash> L</AUTHOR> as listed above. |
304 | |
305 | =head1 LICENSE |
306 | |
307 | This library is free software and may be distributed under the same |
308 | terms as perl itself. |
309 | |
310 | =cut |