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1 | package Package::Variant; |
2 | |
3 | use strictures 1; |
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4 | use Import::Into; |
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5 | use Module::Runtime qw(require_module); |
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6 | use Carp qw(croak); |
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7 | |
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8 | our $VERSION = '1.001004'; # 1.1.4 |
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9 | |
10 | $VERSION = eval $VERSION; |
11 | |
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12 | our %Variable; |
13 | |
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14 | my $sanitize_importing = sub { |
15 | my ($me, $spec) = @_; |
16 | return [] |
17 | unless defined $spec; |
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18 | my @specced = |
19 | not(ref $spec) |
20 | ? ($spec) |
21 | : (ref($spec) eq 'ARRAY') |
22 | ? (@$spec) |
23 | : (ref($spec) eq 'HASH') |
24 | ? (map { |
25 | croak qq{The import argument list for '$_' is not an array ref} |
26 | unless ref($spec->{$_}) eq 'ARRAY'; |
27 | ($_ => $spec->{$_}); |
28 | } sort keys %$spec) |
29 | : croak q{The 'importing' option has to be either a hash or array ref}; |
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30 | my @imports; |
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31 | my $arg_count = 1; |
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32 | while (@specced) { |
33 | my $key = shift @specced; |
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34 | croak qq{Value $arg_count in 'importing' is not a package string}, |
35 | $arg_count |
36 | unless defined($key) and not(ref $key); |
37 | $arg_count++; |
38 | my $import_args = |
39 | (not(@specced) or (defined($specced[0]) and not ref($specced[0]))) |
40 | ? [] |
41 | : (ref($specced[0]) eq 'ARRAY') |
42 | ? do { $arg_count++; shift @specced } |
43 | : croak( |
44 | qq{Value $arg_count for package '$key' in 'importing' is not} |
45 | . qq{ a package string or array ref} |
46 | ); |
47 | push @imports, [$key, $import_args]; |
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48 | } |
49 | return \@imports; |
50 | }; |
51 | |
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52 | my $sub_namer = eval { |
53 | require Sub::Name; sub { shift if @_ > 2; Sub::Name::subname(@_) } |
54 | } || sub { $_[-1] }; |
55 | |
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56 | sub import { |
57 | my $target = caller; |
58 | my $me = shift; |
59 | my $last = (split '::', $target)[-1]; |
60 | my $anon = 'A000'; |
61 | my $variable = $target; |
62 | my %args = @_; |
63 | no strict 'refs'; |
64 | $Variable{$variable} = { |
65 | anon => $anon, |
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66 | args => { |
67 | %args, |
68 | importing => $me->$sanitize_importing($args{importing}), |
69 | }, |
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70 | subs => { |
71 | map +($_ => sub {}), @{$args{subs}||[]}, |
72 | }, |
73 | }; |
74 | *{"${target}::import"} = sub { |
75 | my $target = caller; |
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76 | my (undef, %arg) = @_; |
77 | my $as = defined($arg{as}) ? $arg{as} : $last; |
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78 | no strict 'refs'; |
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79 | *{"${target}::${as}"} = sub { |
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80 | $me->build_variant_of($variable, @_); |
81 | }; |
82 | }; |
83 | my $subs = $Variable{$variable}{subs}; |
84 | foreach my $name (keys %$subs) { |
85 | *{"${target}::${name}"} = sub { |
86 | goto &{$subs->{$name}} |
87 | }; |
88 | } |
89 | *{"${target}::install"} = sub { |
90 | goto &{$Variable{$variable}{install}}; |
91 | } |
92 | } |
93 | |
94 | sub build_variant_of { |
95 | my ($me, $variable, @args) = @_; |
96 | my $variant_name = "${variable}::_Variant_".++$Variable{$variable}{anon}; |
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97 | foreach my $to_import (@{$Variable{$variable}{args}{importing}}) { |
98 | my ($pkg, $args) = @$to_import; |
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99 | require_module $pkg; |
100 | eval q{ BEGIN { $pkg->import::into($variant_name, @{$args}) }; 1; } |
101 | or die $@; |
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102 | } |
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103 | my $subs = $Variable{$variable}{subs}; |
104 | local @{$subs}{keys %$subs} = map $variant_name->can($_), keys %$subs; |
105 | local $Variable{$variable}{install} = sub { |
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106 | my $full_name = "${variant_name}::".shift; |
107 | |
108 | my $ref = $sub_namer->($full_name, @_); |
109 | |
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110 | no strict 'refs'; |
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111 | *$full_name = $ref; |
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112 | }; |
113 | $variable->make_variant($variant_name, @args); |
114 | return $variant_name; |
115 | } |
116 | |
117 | 1; |
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118 | |
119 | __END__ |
120 | |
121 | =head1 NAME |
122 | |
123 | Package::Variant - Parameterizable packages |
124 | |
125 | =head1 SYNOPSIS |
126 | |
127 | # declaring a variable Moo role |
128 | package My::Role::ObjectAttr; |
129 | use strictures 1; |
130 | use Package::Variant |
131 | # what modules to 'use' |
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132 | importing => ['Moo::Role'], |
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133 | # proxied subroutines |
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134 | subs => [ qw(has around before after with) ], |
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135 | |
136 | sub make_variant { |
137 | my ($class, $target_package, %arguments) = @_; |
138 | # access arguments |
139 | my $name = $arguments{name}; |
140 | # use proxied 'has' to add an attribute |
141 | has $name => (is => 'lazy'); |
142 | # install a builder method |
143 | install "_build_${name}" => sub { |
144 | return $arguments{class}->new; |
145 | }; |
146 | } |
147 | |
148 | # using the role |
149 | package My::Class::WithObjectAttr; |
150 | use strictures 1; |
151 | use Moo; |
152 | use My::Role::ObjectAttr; |
153 | |
154 | with ObjectAttr(name => 'some_obj', class => 'Some::Class'); |
155 | |
156 | # using our class |
157 | my $obj = My::Class::WithObjectAttr->new; |
158 | $obj->some_obj; # returns a Some::Class instance |
159 | |
160 | =head1 DESCRIPTION |
161 | |
162 | This module allows you to build packages that return different variations |
163 | depending on what parameters are given. |
164 | |
165 | Users of your package will receive a subroutine able to take parameters |
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166 | and return the name of a suitable variant package. The implementation does |
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167 | not care about what kind of package it builds. |
168 | |
169 | =head2 Declaring a variable package |
170 | |
171 | There are two important parts to creating a variable package. You first |
172 | have to give C<Package::Variant> some basic information about what kind of |
173 | package you want to provide, and how. The second part is implementing a |
174 | method receiving the user's arguments and generating your variants. |
175 | |
176 | =head3 Setting up the environment for building variations |
177 | |
178 | When you C<use Package::Variant>, you pass along some arguments that |
179 | describe how you intend to build your variations. |
180 | |
181 | use Package::Variant |
182 | importing => { $package => \@import_arguments, ... }, |
183 | subs => [ @proxied_subroutine_names ]; |
184 | |
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185 | The L</importing> option needs to be a hash or array reference with |
186 | package names to be C<use>d as keys, and array references containing the |
187 | import arguments as values. These packages will be imported into every new |
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188 | variant, and need to set up every declarative subroutine you require to |
189 | build your variable package. The next option will allow you to use these |
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190 | functions. See L</importing> for more options. You can omit empty import |
191 | argument lists when passing an array reference. |
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192 | |
193 | The L</subs> option is an array reference of subroutine names that are |
194 | exported by the packages specified with L</importing>. These subroutines |
195 | will be proxied from your declaration package to the variant to be |
196 | generated. |
197 | |
198 | With L</importing> initializing your package and L</subs> declaring what |
199 | subroutines you want to use to build a variant, you can now write a |
200 | L</make_variant> method building your variants. |
201 | |
202 | =head3 Declaring a method to produce variants |
203 | |
204 | Every time a user requests a new variant a method named L</make_variant> |
205 | will be called with the name of the target package and the arguments from |
206 | the user. |
207 | |
208 | It can then use the proxied subroutines declared with L</subs> to |
209 | customize the new package. An L</install> subroutine is exported as well |
210 | allowing you to dynamically install methods into the new package. If these |
211 | options aren't flexible enough, you can use the passed name of the new |
212 | package to do any other kind of customizations. |
213 | |
214 | sub make_variant { |
215 | my ($class, $target, @arguments) = @_; |
216 | # ... |
217 | # customization goes here |
218 | # ... |
219 | } |
220 | |
221 | When the method is finished, the user will receive the name of the new |
222 | package variant you just set up. |
223 | |
224 | =head2 Using variable packages |
225 | |
226 | After your variable package is L<created|/Declaring a variable package> |
227 | your users can get a variant generating subroutine by simply importing |
228 | your package. |
229 | |
230 | use My::Variant; |
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231 | my $new_variant_package = Variant(@variant_arguments); |
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232 | |
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233 | The package is now fully initialized and used. You can import the |
234 | subroutine under a different name by specifying an C<as> argument. |
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235 | |
236 | =head2 Dynamic creation of variant packages |
237 | |
238 | For regular uses, the L<normal import|/Using variable packages> provides |
239 | more than enough flexibility. However, if you want to create variations of |
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240 | dynamically determined packages, you can use the L</build_variant_of> |
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241 | method. |
242 | |
243 | You can use this to create variations of other packages and pass arguments |
244 | on to them to allow more modular and extensible variations. |
245 | |
246 | =head1 OPTIONS |
247 | |
248 | These are the options that can be passed when importing |
249 | C<Package::Variant>. They describe the environment in which the variants |
250 | are created. |
251 | |
252 | use Package::Variant |
253 | importing => { $package => \@import_arguments, ... }, |
254 | subs => [ @proxied_subroutines ]; |
255 | |
256 | =head2 importing |
257 | |
258 | This option is a hash reference mapping package names to array references |
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259 | containing import arguments. The packages will be imported with the given |
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260 | arguments by every variation before the L</make_variant> method is asked |
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261 | to create the package (this is done using L<Import::Into>). |
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262 | |
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263 | If import order is important to you, you can also pass the C<importing> |
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264 | arguments as a flat array reference: |
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265 | |
266 | use Package::Variant |
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267 | importing => [ 'PackageA', 'PackageB' ]; |
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268 | |
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269 | # same as |
270 | use Package::Variant |
271 | importing => [ 'PackageA' => [], 'PackageB' => [] ]; |
272 | |
273 | # or |
274 | use Package::Variant |
275 | importing => { 'PackageA' => [], 'PackageB' => [] }; |
276 | |
277 | The import method will be called even if the list of import arguments is |
278 | empty or not specified, |
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279 | |
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280 | If you just want to import a single package's default exports, you can |
281 | also pass a string instead: |
282 | |
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283 | use Package::Variant importing => 'Package'; |
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284 | |
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285 | =head2 subs |
286 | |
287 | An array reference of strings listing the names of subroutines that should |
288 | be proxied. These subroutines are expected to be installed into the new |
289 | variant package by the modules imported with L</importing>. Subroutines |
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290 | with the same name will be available in your declaration package, and will |
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291 | proxy through to the newly created package when used within |
292 | L</make_variant>. |
293 | |
294 | =head1 VARIABLE PACKAGE METHODS |
295 | |
296 | These are methods on the variable package you declare when you import |
297 | C<Package::Variant>. |
298 | |
299 | =head2 make_variant |
300 | |
301 | Some::Variant::Package->make_variant( $target, @arguments ); |
302 | |
303 | B<You need to provide this method.> This method will be called for every |
304 | new variant of your package. This method should use the subroutines |
305 | declared in L</subs> to customize the new variant package. |
306 | |
307 | This is a class method receiving the C<$target> package and the |
308 | C<@arguments> defining the requested variant. |
309 | |
310 | =head2 import |
311 | |
312 | use Some::Variant::Package; |
313 | my $variant_package = Package( @arguments ); |
314 | |
315 | This method is provided for you. It will allow a user to C<use> your |
316 | package and receive a subroutine taking C<@arguments> defining the variant |
317 | and returning the name of the newly created variant package. |
318 | |
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319 | The following options can be specified when importing: |
320 | |
321 | =over |
322 | |
323 | =item * B<as> |
324 | |
325 | use Some::Variant::Package as => 'Foo'; |
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326 | my $variant_package = Foo(@arguments); |
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327 | |
328 | Exports the generator subroutine under a different name than the default. |
329 | |
330 | =back |
331 | |
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332 | =head1 C<Package::Variant> METHODS |
333 | |
334 | These methods are available on C<Package::Variant> itself. |
335 | |
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336 | =head2 build_variant_of |
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337 | |
338 | my $variant_package = Package::Variant |
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339 | ->build_variant_of($variable_package, @arguments); |
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340 | |
341 | This is the dynamic method of creating new variants. It takes the |
342 | C<$variable_package>, which is a pre-declared variable package, and a set |
343 | of C<@arguments> passed to the package to generate a new |
344 | C<$variant_package>, which will be returned. |
345 | |
346 | =head2 import |
347 | |
348 | use Package::Variant @options; |
349 | |
350 | Sets up the environment in which you declare the variants of your |
351 | packages. See L</OPTIONS> for details on the available options and |
352 | L</EXPORTS> for a list of exported subroutines. |
353 | |
354 | =head1 EXPORTS |
355 | |
356 | Additionally to the proxies for subroutines provided in L</subs>, the |
357 | following exports will be available in your variable package: |
358 | |
359 | =head2 install |
360 | |
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361 | install($method_name, $code_reference); |
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362 | |
363 | Installs a method with the given C<$method_name> into the newly created |
364 | variant package. The C<$code_reference> will be used as the body for the |
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365 | method, and if L<Sub::Name> is available the coderef will be named. If you |
366 | want to name it something else, then use: |
367 | |
368 | install($method_name, $name_to_use, $code_reference); |
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369 | |
370 | =head1 AUTHOR |
371 | |
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372 | mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk> |
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373 | |
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374 | =head1 CONTRIBUTORS |
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375 | |
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376 | phaylon - Robert Sedlacek (cpan:PHAYLON) <r.sedlacek@shadowcat.co.uk> |
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377 | |
378 | =head1 COPYRIGHT |
379 | |
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380 | Copyright (c) 2010-2012 the C<Package::Variant> L</AUTHOR> and |
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381 | L</CONTRIBUTORS> as listed above. |
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382 | |
383 | =head1 LICENSE |
384 | |
385 | This library is free software and may be distributed under the same |
386 | terms as perl itself. |
387 | |
388 | =cut |