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236a4386 |
1 | package Package::Variant; |
2 | |
3 | use strictures 1; |
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4 | use Import::Into; |
3c1ca277 |
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 = '1.002002'; |
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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; |
203d81fc |
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; |
203d81fc |
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 { |
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57 | my $variable = caller; |
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58 | my $me = shift; |
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59 | my $last = (split '::', $variable)[-1]; |
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60 | my $anon = 'A000'; |
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61 | my %args = @_; |
62 | no strict 'refs'; |
63 | $Variable{$variable} = { |
64 | anon => $anon, |
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65 | args => { |
66 | %args, |
67 | importing => $me->$sanitize_importing($args{importing}), |
68 | }, |
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69 | subs => { |
70 | map +($_ => sub {}), @{$args{subs}||[]}, |
71 | }, |
72 | }; |
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73 | *{"${variable}::import"} = sub { |
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74 | my $target = caller; |
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75 | my (undef, %arg) = @_; |
76 | my $as = defined($arg{as}) ? $arg{as} : $last; |
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77 | no strict 'refs'; |
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78 | *{"${target}::${as}"} = sub { |
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79 | $me->build_variant_of($variable, @_); |
80 | }; |
81 | }; |
82 | my $subs = $Variable{$variable}{subs}; |
83 | foreach my $name (keys %$subs) { |
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84 | *{"${variable}::${name}"} = sub { |
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85 | goto &{$subs->{$name}} |
86 | }; |
87 | } |
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88 | *{"${variable}::install"} = sub { |
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89 | goto &{$Variable{$variable}{install}}; |
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90 | }; |
91 | *{"${variable}::build_variant"} = sub { |
92 | shift; |
93 | $me->build_variant_of($variable, @_); |
94 | }; |
236a4386 |
95 | } |
96 | |
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97 | sub build_variant_package_name { |
98 | my ($me, $variable, @args) = @_; |
99 | if ($variable->can('make_variant_package_name')) { |
100 | return $variable->make_variant_package_name(@args); |
101 | } |
102 | return "${variable}::_Variant_".++$Variable{$variable}{anon}; |
103 | } |
104 | |
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105 | sub build_variant_of { |
106 | my ($me, $variable, @args) = @_; |
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107 | my $variant_name = $me->build_variant_package_name($variable, @args); |
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108 | foreach my $to_import (@{$Variable{$variable}{args}{importing}}) { |
109 | my ($pkg, $args) = @$to_import; |
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110 | require_module $pkg; |
111 | eval q{ BEGIN { $pkg->import::into($variant_name, @{$args}) }; 1; } |
112 | or die $@; |
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113 | } |
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114 | my $subs = $Variable{$variable}{subs}; |
115 | local @{$subs}{keys %$subs} = map $variant_name->can($_), keys %$subs; |
116 | local $Variable{$variable}{install} = sub { |
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117 | my $full_name = "${variant_name}::".shift; |
118 | |
119 | my $ref = $sub_namer->($full_name, @_); |
120 | |
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121 | no strict 'refs'; |
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122 | *$full_name = $ref; |
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123 | }; |
124 | $variable->make_variant($variant_name, @args); |
125 | return $variant_name; |
126 | } |
127 | |
128 | 1; |
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129 | |
130 | __END__ |
131 | |
132 | =head1 NAME |
133 | |
134 | Package::Variant - Parameterizable packages |
135 | |
136 | =head1 SYNOPSIS |
137 | |
138 | # declaring a variable Moo role |
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139 | package My::VariableRole::ObjectAttr; |
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140 | use strictures 1; |
141 | use Package::Variant |
142 | # what modules to 'use' |
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143 | importing => ['Moo::Role'], |
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144 | # proxied subroutines |
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145 | subs => [ qw(has around before after with) ]; |
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146 | |
147 | sub make_variant { |
148 | my ($class, $target_package, %arguments) = @_; |
149 | # access arguments |
150 | my $name = $arguments{name}; |
151 | # use proxied 'has' to add an attribute |
152 | has $name => (is => 'lazy'); |
153 | # install a builder method |
154 | install "_build_${name}" => sub { |
155 | return $arguments{class}->new; |
156 | }; |
157 | } |
158 | |
159 | # using the role |
160 | package My::Class::WithObjectAttr; |
161 | use strictures 1; |
162 | use Moo; |
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163 | use My::VariableRole::ObjectAttr; |
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164 | |
165 | with ObjectAttr(name => 'some_obj', class => 'Some::Class'); |
166 | |
167 | # using our class |
168 | my $obj = My::Class::WithObjectAttr->new; |
169 | $obj->some_obj; # returns a Some::Class instance |
170 | |
171 | =head1 DESCRIPTION |
172 | |
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173 | This module allows you to build a variable package that contains a package |
174 | template and can use it to build variant packages at runtime. |
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175 | |
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176 | Your variable package will export a subroutine which will build a variant |
177 | package, combining its arguments with the template, and return the name of the |
178 | new variant package. |
179 | |
180 | The implementation does not care about what kind of packages it builds, be they |
181 | simple function exporters, classes, singletons or something entirely different. |
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182 | |
183 | =head2 Declaring a variable package |
184 | |
185 | There are two important parts to creating a variable package. You first |
186 | have to give C<Package::Variant> some basic information about what kind of |
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187 | variant packages you want to provide, and how. The second part is implementing a |
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188 | method which builds the components of the variant packages that use the user's |
189 | arguments or cannot be provided with a static import. |
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190 | |
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191 | =head3 Setting up the environment for building variants |
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192 | |
193 | When you C<use Package::Variant>, you pass along some arguments that |
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194 | describe how you intend to build your variants. |
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195 | |
196 | use Package::Variant |
197 | importing => { $package => \@import_arguments, ... }, |
198 | subs => [ @proxied_subroutine_names ]; |
199 | |
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200 | The L</importing> option needs to be a hash or array reference with |
201 | package names to be C<use>d as keys, and array references containing the |
202 | import arguments as values. These packages will be imported into every new |
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203 | variant package, to provide static functionality of the variant packages and to |
204 | set up every declarative subroutine you require to build variants package |
205 | components. The next option will allow you to use these functions. See |
206 | L</importing> for more options. You can omit empty import argument lists when |
207 | passing an array reference. |
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208 | |
209 | The L</subs> option is an array reference of subroutine names that are |
210 | exported by the packages specified with L</importing>. These subroutines |
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211 | will be proxied from your variable package to the variant to be |
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212 | generated. |
213 | |
214 | With L</importing> initializing your package and L</subs> declaring what |
215 | subroutines you want to use to build a variant, you can now write a |
216 | L</make_variant> method building your variants. |
217 | |
218 | =head3 Declaring a method to produce variants |
219 | |
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220 | Every time a user requests a new variant, a method named L</make_variant> |
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221 | will be called with the name of the target package and the arguments from |
222 | the user. |
223 | |
224 | It can then use the proxied subroutines declared with L</subs> to |
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225 | customize the variant package. An L</install> subroutine is exported as well |
226 | allowing you to dynamically install methods into the variant package. If these |
227 | options aren't flexible enough, you can use the passed name of the variant |
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228 | package to do any other kind of customizations. |
229 | |
230 | sub make_variant { |
231 | my ($class, $target, @arguments) = @_; |
232 | # ... |
233 | # customization goes here |
234 | # ... |
235 | } |
236 | |
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237 | When the method is finished, the user will receive the name of the new variant |
238 | package you just set up. |
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239 | |
240 | =head2 Using variable packages |
241 | |
242 | After your variable package is L<created|/Declaring a variable package> |
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243 | your users can get a variant generator subroutine by simply importing |
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244 | your package. |
245 | |
246 | use My::Variant; |
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247 | my $new_variant_package = Variant(@variant_arguments); |
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248 | # the variant package is now fully initialized and used |
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249 | |
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250 | You can import the subroutine under a different name by specifying an C<as> |
251 | argument. |
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252 | |
253 | =head2 Dynamic creation of variant packages |
254 | |
255 | For regular uses, the L<normal import|/Using variable packages> provides |
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256 | more than enough flexibility. However, if you want to create variants of |
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257 | dynamically determined packages, you can use the L</build_variant_of> |
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258 | method. |
259 | |
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260 | You can use this to create variants of other packages and pass arguments |
261 | on to them to allow more modular and extensible variants. |
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262 | |
263 | =head1 OPTIONS |
264 | |
265 | These are the options that can be passed when importing |
266 | C<Package::Variant>. They describe the environment in which the variants |
267 | are created. |
268 | |
269 | use Package::Variant |
270 | importing => { $package => \@import_arguments, ... }, |
271 | subs => [ @proxied_subroutines ]; |
272 | |
273 | =head2 importing |
274 | |
275 | This option is a hash reference mapping package names to array references |
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276 | containing import arguments. The packages will be imported with the given |
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277 | arguments by every variant before the L</make_variant> method is asked |
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278 | to create the package (this is done using L<Import::Into>). |
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279 | |
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280 | If import order is important to you, you can also pass the C<importing> |
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281 | arguments as a flat array reference: |
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282 | |
283 | use Package::Variant |
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284 | importing => [ 'PackageA', 'PackageB' ]; |
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285 | |
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286 | # same as |
287 | use Package::Variant |
288 | importing => [ 'PackageA' => [], 'PackageB' => [] ]; |
289 | |
290 | # or |
291 | use Package::Variant |
292 | importing => { 'PackageA' => [], 'PackageB' => [] }; |
293 | |
294 | The import method will be called even if the list of import arguments is |
295 | empty or not specified, |
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296 | |
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297 | If you just want to import a single package's default exports, you can |
298 | also pass a string instead: |
299 | |
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300 | use Package::Variant importing => 'Package'; |
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301 | |
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302 | =head2 subs |
303 | |
304 | An array reference of strings listing the names of subroutines that should |
305 | be proxied. These subroutines are expected to be installed into the new |
306 | variant package by the modules imported with L</importing>. Subroutines |
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307 | with the same name will be available in your variable package, and will |
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308 | proxy through to the newly created package when used within |
309 | L</make_variant>. |
310 | |
311 | =head1 VARIABLE PACKAGE METHODS |
312 | |
313 | These are methods on the variable package you declare when you import |
314 | C<Package::Variant>. |
315 | |
316 | =head2 make_variant |
317 | |
318 | Some::Variant::Package->make_variant( $target, @arguments ); |
319 | |
320 | B<You need to provide this method.> This method will be called for every |
321 | new variant of your package. This method should use the subroutines |
322 | declared in L</subs> to customize the new variant package. |
323 | |
324 | This is a class method receiving the C<$target> package and the |
325 | C<@arguments> defining the requested variant. |
326 | |
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327 | =head2 make_variant_package_name |
328 | |
329 | Some::Variant::Package->make_variant_package_name( @arguments ); |
330 | |
331 | B<You may optionally provide this method.> If present, this method will be |
332 | used to determine the package name for a particular variant being constructed. |
333 | |
334 | If you do not implement it, a unique package name something like |
335 | |
336 | Some::Variant::Package::_Variant_A003 |
337 | |
338 | will be created for you. |
339 | |
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340 | =head2 import |
341 | |
342 | use Some::Variant::Package; |
343 | my $variant_package = Package( @arguments ); |
344 | |
345 | This method is provided for you. It will allow a user to C<use> your |
346 | package and receive a subroutine taking C<@arguments> defining the variant |
347 | and returning the name of the newly created variant package. |
348 | |
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349 | The following options can be specified when importing: |
350 | |
351 | =over |
352 | |
353 | =item * B<as> |
354 | |
355 | use Some::Variant::Package as => 'Foo'; |
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356 | my $variant_package = Foo(@arguments); |
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357 | |
358 | Exports the generator subroutine under a different name than the default. |
359 | |
360 | =back |
361 | |
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362 | =head2 build_variant |
363 | |
364 | use Some::Variant::Package (); |
365 | my $variant_package = Some::Variant::Package->build_variant( @arguments ); |
366 | |
367 | This method is provided for you. It will generate a variant package |
368 | and return its name, just like the generator sub provided by |
369 | L</import>. This allows you to avoid importing anything into the |
370 | consuming package. |
371 | |
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372 | =head1 C<Package::Variant> METHODS |
373 | |
374 | These methods are available on C<Package::Variant> itself. |
375 | |
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376 | =head2 build_variant_of |
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377 | |
378 | my $variant_package = Package::Variant |
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379 | ->build_variant_of($variable_package, @arguments); |
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380 | |
381 | This is the dynamic method of creating new variants. It takes the |
382 | C<$variable_package>, which is a pre-declared variable package, and a set |
383 | of C<@arguments> passed to the package to generate a new |
384 | C<$variant_package>, which will be returned. |
385 | |
386 | =head2 import |
387 | |
388 | use Package::Variant @options; |
389 | |
390 | Sets up the environment in which you declare the variants of your |
391 | packages. See L</OPTIONS> for details on the available options and |
392 | L</EXPORTS> for a list of exported subroutines. |
393 | |
394 | =head1 EXPORTS |
395 | |
396 | Additionally to the proxies for subroutines provided in L</subs>, the |
397 | following exports will be available in your variable package: |
398 | |
399 | =head2 install |
400 | |
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401 | install($method_name, $code_reference); |
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402 | |
403 | Installs a method with the given C<$method_name> into the newly created |
404 | variant package. The C<$code_reference> will be used as the body for the |
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405 | method, and if L<Sub::Name> is available the coderef will be named. If you |
406 | want to name it something else, then use: |
407 | |
408 | install($method_name, $name_to_use, $code_reference); |
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409 | |
410 | =head1 AUTHOR |
411 | |
5b1d922a |
412 | mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk> |
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413 | |
5b1d922a |
414 | =head1 CONTRIBUTORS |
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415 | |
5b1d922a |
416 | phaylon - Robert Sedlacek (cpan:PHAYLON) <r.sedlacek@shadowcat.co.uk> |
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417 | |
39c3689b |
418 | haarg - Graham Knop (cpan:HAARG) <haarg@haarg.org> |
419 | |
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420 | =head1 COPYRIGHT |
421 | |
2b728d4c |
422 | Copyright (c) 2010-2012 the C<Package::Variant> L</AUTHOR> and |
57114c43 |
423 | L</CONTRIBUTORS> as listed above. |
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424 | |
425 | =head1 LICENSE |
426 | |
427 | This library is free software and may be distributed under the same |
428 | terms as perl itself. |
429 | |
430 | =cut |