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1 | package Package::Variant; |
2 | |
3 | use strictures 1; |
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4 | use Carp qw( croak ); |
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5 | |
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6 | our $VERSION = '1.000000'; # 1.0.0 |
7 | |
8 | $VERSION = eval $VERSION; |
9 | |
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10 | our %Variable; |
11 | |
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12 | my $sanitize_importing = sub { |
13 | my ($me, $spec) = @_; |
14 | return [] |
15 | unless defined $spec; |
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16 | my @specced = |
17 | not(ref $spec) |
18 | ? ($spec) |
19 | : (ref($spec) eq 'ARRAY') |
20 | ? (@$spec) |
21 | : (ref($spec) eq 'HASH') |
22 | ? (map { |
23 | croak qq{The import argument list for '$_' is not an array ref} |
24 | unless ref($spec->{$_}) eq 'ARRAY'; |
25 | ($_ => $spec->{$_}); |
26 | } sort keys %$spec) |
27 | : croak q{The 'importing' option has to be either a hash or array ref}; |
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28 | my @imports; |
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29 | my $arg_count = 1; |
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30 | while (@specced) { |
31 | my $key = shift @specced; |
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32 | croak qq{Value $arg_count in 'importing' is not a package string}, |
33 | $arg_count |
34 | unless defined($key) and not(ref $key); |
35 | $arg_count++; |
36 | my $import_args = |
37 | (not(@specced) or (defined($specced[0]) and not ref($specced[0]))) |
38 | ? [] |
39 | : (ref($specced[0]) eq 'ARRAY') |
40 | ? do { $arg_count++; shift @specced } |
41 | : croak( |
42 | qq{Value $arg_count for package '$key' in 'importing' is not} |
43 | . qq{ a package string or array ref} |
44 | ); |
45 | push @imports, [$key, $import_args]; |
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46 | } |
47 | return \@imports; |
48 | }; |
49 | |
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50 | sub import { |
51 | my $target = caller; |
52 | my $me = shift; |
53 | my $last = (split '::', $target)[-1]; |
54 | my $anon = 'A000'; |
55 | my $variable = $target; |
56 | my %args = @_; |
57 | no strict 'refs'; |
58 | $Variable{$variable} = { |
59 | anon => $anon, |
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60 | args => { |
61 | %args, |
62 | importing => $me->$sanitize_importing($args{importing}), |
63 | }, |
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64 | subs => { |
65 | map +($_ => sub {}), @{$args{subs}||[]}, |
66 | }, |
67 | }; |
68 | *{"${target}::import"} = sub { |
69 | my $target = caller; |
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70 | my (undef, %arg) = @_; |
71 | my $as = defined($arg{as}) ? $arg{as} : $last; |
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72 | no strict 'refs'; |
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73 | *{"${target}::${as}"} = sub { |
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74 | $me->build_variant_of($variable, @_); |
75 | }; |
76 | }; |
77 | my $subs = $Variable{$variable}{subs}; |
78 | foreach my $name (keys %$subs) { |
79 | *{"${target}::${name}"} = sub { |
80 | goto &{$subs->{$name}} |
81 | }; |
82 | } |
83 | *{"${target}::install"} = sub { |
84 | goto &{$Variable{$variable}{install}}; |
85 | } |
86 | } |
87 | |
88 | sub build_variant_of { |
89 | my ($me, $variable, @args) = @_; |
90 | my $variant_name = "${variable}::_Variant_".++$Variable{$variable}{anon}; |
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91 | my $import = $Variable{$variable}{args}{importing}; |
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92 | my $setup = join("\n", |
93 | "package ${variant_name};", |
94 | (map sprintf( |
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95 | q!use %s %s;!, |
96 | $import->[$_][0], |
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97 | scalar(@{$import->[$_][1]}) |
98 | ? sprintf( |
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99 | q!@{$import->[%d][1]}!, |
100 | $_, |
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101 | ) |
102 | : '', |
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103 | ), 0..$#$import), |
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104 | "1;", |
105 | ); |
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106 | eval $setup |
107 | or die "evaling ${setup} failed: $@"; |
108 | my $subs = $Variable{$variable}{subs}; |
109 | local @{$subs}{keys %$subs} = map $variant_name->can($_), keys %$subs; |
110 | local $Variable{$variable}{install} = sub { |
111 | my ($name, $ref) = @_; |
112 | no strict 'refs'; |
113 | *{"${variant_name}::${name}"} = $ref; |
114 | }; |
115 | $variable->make_variant($variant_name, @args); |
116 | return $variant_name; |
117 | } |
118 | |
119 | 1; |
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120 | |
121 | __END__ |
122 | |
123 | =head1 NAME |
124 | |
125 | Package::Variant - Parameterizable packages |
126 | |
127 | =head1 SYNOPSIS |
128 | |
129 | # declaring a variable Moo role |
130 | package My::Role::ObjectAttr; |
131 | use strictures 1; |
132 | use Package::Variant |
133 | # what modules to 'use' |
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134 | importing => ['Moo::Role'], |
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135 | # proxied subroutines |
136 | subs => [qw( has around before after extends )], |
137 | |
138 | sub make_variant { |
139 | my ($class, $target_package, %arguments) = @_; |
140 | # access arguments |
141 | my $name = $arguments{name}; |
142 | # use proxied 'has' to add an attribute |
143 | has $name => (is => 'lazy'); |
144 | # install a builder method |
145 | install "_build_${name}" => sub { |
146 | return $arguments{class}->new; |
147 | }; |
148 | } |
149 | |
150 | # using the role |
151 | package My::Class::WithObjectAttr; |
152 | use strictures 1; |
153 | use Moo; |
154 | use My::Role::ObjectAttr; |
155 | |
156 | with ObjectAttr(name => 'some_obj', class => 'Some::Class'); |
157 | |
158 | # using our class |
159 | my $obj = My::Class::WithObjectAttr->new; |
160 | $obj->some_obj; # returns a Some::Class instance |
161 | |
162 | =head1 DESCRIPTION |
163 | |
164 | This module allows you to build packages that return different variations |
165 | depending on what parameters are given. |
166 | |
167 | Users of your package will receive a subroutine able to take parameters |
168 | and return the name of a suitable variant package. The implmenetation does |
169 | not care about what kind of package it builds. |
170 | |
171 | =head2 Declaring a variable package |
172 | |
173 | There are two important parts to creating a variable package. You first |
174 | have to give C<Package::Variant> some basic information about what kind of |
175 | package you want to provide, and how. The second part is implementing a |
176 | method receiving the user's arguments and generating your variants. |
177 | |
178 | =head3 Setting up the environment for building variations |
179 | |
180 | When you C<use Package::Variant>, you pass along some arguments that |
181 | describe how you intend to build your variations. |
182 | |
183 | use Package::Variant |
184 | importing => { $package => \@import_arguments, ... }, |
185 | subs => [ @proxied_subroutine_names ]; |
186 | |
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187 | The L</importing> option needs to be a hash or array reference with |
188 | package names to be C<use>d as keys, and array references containing the |
189 | import arguments as values. These packages will be imported into every new |
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190 | variant, and need to set up every declarative subroutine you require to |
191 | build your variable package. The next option will allow you to use these |
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192 | functions. See L</importing> for more options. You can omit empty import |
193 | argument lists when passing an array reference. |
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194 | |
195 | The L</subs> option is an array reference of subroutine names that are |
196 | exported by the packages specified with L</importing>. These subroutines |
197 | will be proxied from your declaration package to the variant to be |
198 | generated. |
199 | |
200 | With L</importing> initializing your package and L</subs> declaring what |
201 | subroutines you want to use to build a variant, you can now write a |
202 | L</make_variant> method building your variants. |
203 | |
204 | =head3 Declaring a method to produce variants |
205 | |
206 | Every time a user requests a new variant a method named L</make_variant> |
207 | will be called with the name of the target package and the arguments from |
208 | the user. |
209 | |
210 | It can then use the proxied subroutines declared with L</subs> to |
211 | customize the new package. An L</install> subroutine is exported as well |
212 | allowing you to dynamically install methods into the new package. If these |
213 | options aren't flexible enough, you can use the passed name of the new |
214 | package to do any other kind of customizations. |
215 | |
216 | sub make_variant { |
217 | my ($class, $target, @arguments) = @_; |
218 | # ... |
219 | # customization goes here |
220 | # ... |
221 | } |
222 | |
223 | When the method is finished, the user will receive the name of the new |
224 | package variant you just set up. |
225 | |
226 | =head2 Using variable packages |
227 | |
228 | After your variable package is L<created|/Declaring a variable package> |
229 | your users can get a variant generating subroutine by simply importing |
230 | your package. |
231 | |
232 | use My::Variant; |
233 | my $new_variant_package = Variant( @variant_arguments ); |
234 | |
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235 | The package is now fully initialized and used. You can import the |
236 | subroutine under a different name by specifying an C<as> argument. |
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237 | |
238 | =head2 Dynamic creation of variant packages |
239 | |
240 | For regular uses, the L<normal import|/Using variable packages> provides |
241 | more than enough flexibility. However, if you want to create variations of |
242 | dynamically determined packages, you can use the L</build_variation_of> |
243 | method. |
244 | |
245 | You can use this to create variations of other packages and pass arguments |
246 | on to them to allow more modular and extensible variations. |
247 | |
248 | =head1 OPTIONS |
249 | |
250 | These are the options that can be passed when importing |
251 | C<Package::Variant>. They describe the environment in which the variants |
252 | are created. |
253 | |
254 | use Package::Variant |
255 | importing => { $package => \@import_arguments, ... }, |
256 | subs => [ @proxied_subroutines ]; |
257 | |
258 | =head2 importing |
259 | |
260 | This option is a hash reference mapping package names to array references |
261 | containing import arguments. The packages will be C<use>d with the given |
262 | arguments by every variation before the L</make_variant> method is asked |
263 | to create the package. |
264 | |
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265 | If import order is important to you, you can also pass the C<importing> |
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266 | arguments as a flat array reference: |
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267 | |
268 | use Package::Variant |
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269 | importing => [ 'PackageA', 'PackageB' ]; |
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270 | |
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271 | # same as |
272 | use Package::Variant |
273 | importing => [ 'PackageA' => [], 'PackageB' => [] ]; |
274 | |
275 | # or |
276 | use Package::Variant |
277 | importing => { 'PackageA' => [], 'PackageB' => [] }; |
278 | |
279 | The import method will be called even if the list of import arguments is |
280 | empty or not specified, |
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281 | |
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282 | If you just want to import a single package's default exports, you can |
283 | also pass a string instead: |
284 | |
285 | use PAckage::Variant importing => 'Package'; |
286 | |
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287 | =head2 subs |
288 | |
289 | An array reference of strings listing the names of subroutines that should |
290 | be proxied. These subroutines are expected to be installed into the new |
291 | variant package by the modules imported with L</importing>. Subroutines |
292 | with the same name will be availabe in your declaration package, and will |
293 | proxy through to the newly created package when used within |
294 | L</make_variant>. |
295 | |
296 | =head1 VARIABLE PACKAGE METHODS |
297 | |
298 | These are methods on the variable package you declare when you import |
299 | C<Package::Variant>. |
300 | |
301 | =head2 make_variant |
302 | |
303 | Some::Variant::Package->make_variant( $target, @arguments ); |
304 | |
305 | B<You need to provide this method.> This method will be called for every |
306 | new variant of your package. This method should use the subroutines |
307 | declared in L</subs> to customize the new variant package. |
308 | |
309 | This is a class method receiving the C<$target> package and the |
310 | C<@arguments> defining the requested variant. |
311 | |
312 | =head2 import |
313 | |
314 | use Some::Variant::Package; |
315 | my $variant_package = Package( @arguments ); |
316 | |
317 | This method is provided for you. It will allow a user to C<use> your |
318 | package and receive a subroutine taking C<@arguments> defining the variant |
319 | and returning the name of the newly created variant package. |
320 | |
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321 | The following options can be specified when importing: |
322 | |
323 | =over |
324 | |
325 | =item * B<as> |
326 | |
327 | use Some::Variant::Package as => 'Foo'; |
328 | my $variant_package = Foo( @arguments ); |
329 | |
330 | Exports the generator subroutine under a different name than the default. |
331 | |
332 | =back |
333 | |
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334 | =head1 C<Package::Variant> METHODS |
335 | |
336 | These methods are available on C<Package::Variant> itself. |
337 | |
338 | =head2 build_variation_of |
339 | |
340 | my $variant_package = Package::Variant |
341 | ->build_variation_of( $variable_package, @arguments ); |
342 | |
343 | This is the dynamic method of creating new variants. It takes the |
344 | C<$variable_package>, which is a pre-declared variable package, and a set |
345 | of C<@arguments> passed to the package to generate a new |
346 | C<$variant_package>, which will be returned. |
347 | |
348 | =head2 import |
349 | |
350 | use Package::Variant @options; |
351 | |
352 | Sets up the environment in which you declare the variants of your |
353 | packages. See L</OPTIONS> for details on the available options and |
354 | L</EXPORTS> for a list of exported subroutines. |
355 | |
356 | =head1 EXPORTS |
357 | |
358 | Additionally to the proxies for subroutines provided in L</subs>, the |
359 | following exports will be available in your variable package: |
360 | |
361 | =head2 install |
362 | |
363 | install( $method_name, $code_reference ); |
364 | |
365 | Installs a method with the given C<$method_name> into the newly created |
366 | variant package. The C<$code_reference> will be used as the body for the |
367 | method. |
368 | |
369 | =head1 AUTHOR |
370 | |
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371 | mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk> |
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372 | |
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373 | =head1 CONTRIBUTORS |
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374 | |
5b1d922a |
375 | phaylon - Robert Sedlacek (cpan:PHAYLON) <r.sedlacek@shadowcat.co.uk> |
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376 | |
377 | =head1 COPYRIGHT |
378 | |
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379 | Copyright (c) 2010-2011 the C<Package::Variant> L</AUTHOR> and |
380 | L</CONTRIBUTORS> as listed above. |
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381 | |
382 | =head1 LICENSE |
383 | |
384 | This library is free software and may be distributed under the same |
385 | terms as perl itself. |
386 | |
387 | =cut |