1 package Package::Variant;
4 use Module::Runtime qw(require_module module_notional_filename);
7 our $VERSION = '1.002000'; # 1.2.0
9 $VERSION = eval $VERSION;
13 my $sanitize_importing = sub {
20 : (ref($spec) eq 'ARRAY')
22 : (ref($spec) eq 'HASH')
24 croak qq{The import argument list for '$_' is not an array ref}
25 unless ref($spec->{$_}) eq 'ARRAY';
28 : croak q{The 'importing' option has to be either a hash or array ref};
32 my $key = shift @specced;
33 croak qq{Value $arg_count in 'importing' is not a package string},
35 unless defined($key) and not(ref $key);
38 (not(@specced) or (defined($specced[0]) and not ref($specced[0])))
40 : (ref($specced[0]) eq 'ARRAY')
41 ? do { $arg_count++; shift @specced }
43 qq{Value $arg_count for package '$key' in 'importing' is not}
44 . qq{ a package string or array ref}
46 push @imports, [$key, $import_args];
51 my $sub_namer = eval {
52 require Sub::Name; sub { shift if @_ > 2; Sub::Name::subname(@_) }
56 my $variable = caller;
58 my $last = (split '::', $variable)[-1];
62 $Variable{$variable} = {
66 importing => $me->$sanitize_importing($args{importing}),
69 map +($_ => sub {}), @{$args{subs}||[]},
72 *{"${variable}::import"} = sub {
74 my (undef, %arg) = @_;
75 my $as = defined($arg{as}) ? $arg{as} : $last;
77 *{"${target}::${as}"} = sub {
78 $me->build_variant_of($variable, @_);
81 my $subs = $Variable{$variable}{subs};
82 foreach my $name (keys %$subs) {
83 *{"${variable}::${name}"} = sub {
84 goto &{$subs->{$name}}
87 *{"${variable}::install"} = sub {
88 goto &{$Variable{$variable}{install}};
90 *{"${variable}::build_variant"} = sub {
92 $me->build_variant_of($variable, @_);
96 sub build_variant_of {
97 my ($me, $variable, @args) = @_;
98 my $variant_name = "${variable}::_Variant_".++$Variable{$variable}{anon};
99 my $build = "package $variant_name;\n";
100 my $importing = $Variable{$variable}{args}{importing};
101 foreach my $i (0 .. $#$importing) {
102 my $pkg = $importing->[$i][0];
103 $build .= "use $pkg \@{\$importing->[$i][1]};\n";
105 my $subs = $Variable{$variable}{subs};
107 local @{$subs}{keys %$subs} = map $variant_name->can($_), keys %$subs;
108 local $Variable{$variable}{install} = sub {
109 my $full_name = "${variant_name}::".shift;
111 my $ref = $sub_namer->($full_name, @_);
116 $variable->make_variant($variant_name, @args);
118 $build .= "BEGIN { \$builder->() }\n1;\n";
119 eval $build or die $@;
120 $INC{module_notional_filename($variant_name)} = '(built by Package::Variant)';
121 return $variant_name;
130 Package::Variant - Parameterizable packages
134 # declaring a variable Moo role
135 package My::Role::ObjectAttr;
138 # what modules to 'use'
139 importing => ['Moo::Role'],
140 # proxied subroutines
141 subs => [ qw(has around before after with) ],
144 my ($class, $target_package, %arguments) = @_;
146 my $name = $arguments{name};
147 # use proxied 'has' to add an attribute
148 has $name => (is => 'lazy');
149 # install a builder method
150 install "_build_${name}" => sub {
151 return $arguments{class}->new;
156 package My::Class::WithObjectAttr;
159 use My::Role::ObjectAttr;
161 with ObjectAttr(name => 'some_obj', class => 'Some::Class');
164 my $obj = My::Class::WithObjectAttr->new;
165 $obj->some_obj; # returns a Some::Class instance
169 This module allows you to build packages that return different variations
170 depending on what parameters are given.
172 Users of your package will receive a subroutine able to take parameters
173 and return the name of a suitable variant package. The implementation does
174 not care about what kind of package it builds.
176 =head2 Declaring a variable package
178 There are two important parts to creating a variable package. You first
179 have to give C<Package::Variant> some basic information about what kind of
180 package you want to provide, and how. The second part is implementing a
181 method receiving the user's arguments and generating your variants.
183 =head3 Setting up the environment for building variations
185 When you C<use Package::Variant>, you pass along some arguments that
186 describe how you intend to build your variations.
189 importing => { $package => \@import_arguments, ... },
190 subs => [ @proxied_subroutine_names ];
192 The L</importing> option needs to be a hash or array reference with
193 package names to be C<use>d as keys, and array references containing the
194 import arguments as values. These packages will be imported into every new
195 variant, and need to set up every declarative subroutine you require to
196 build your variable package. The next option will allow you to use these
197 functions. See L</importing> for more options. You can omit empty import
198 argument lists when passing an array reference.
200 The L</subs> option is an array reference of subroutine names that are
201 exported by the packages specified with L</importing>. These subroutines
202 will be proxied from your declaration package to the variant to be
205 With L</importing> initializing your package and L</subs> declaring what
206 subroutines you want to use to build a variant, you can now write a
207 L</make_variant> method building your variants.
209 =head3 Declaring a method to produce variants
211 Every time a user requests a new variant a method named L</make_variant>
212 will be called with the name of the target package and the arguments from
215 It can then use the proxied subroutines declared with L</subs> to
216 customize the new package. An L</install> subroutine is exported as well
217 allowing you to dynamically install methods into the new package. If these
218 options aren't flexible enough, you can use the passed name of the new
219 package to do any other kind of customizations.
222 my ($class, $target, @arguments) = @_;
224 # customization goes here
228 When the method is finished, the user will receive the name of the new
229 package variant you just set up.
231 =head2 Using variable packages
233 After your variable package is L<created|/Declaring a variable package>
234 your users can get a variant generating subroutine by simply importing
238 my $new_variant_package = Variant(@variant_arguments);
240 The package is now fully initialized and used. You can import the
241 subroutine under a different name by specifying an C<as> argument.
243 =head2 Dynamic creation of variant packages
245 For regular uses, the L<normal import|/Using variable packages> provides
246 more than enough flexibility. However, if you want to create variations of
247 dynamically determined packages, you can use the L</build_variant_of>
250 You can use this to create variations of other packages and pass arguments
251 on to them to allow more modular and extensible variations.
255 These are the options that can be passed when importing
256 C<Package::Variant>. They describe the environment in which the variants
260 importing => { $package => \@import_arguments, ... },
261 subs => [ @proxied_subroutines ];
265 This option is a hash reference mapping package names to array references
266 containing import arguments. The packages will be imported with the given
267 arguments by every variation before the L</make_variant> method is asked
268 to create the package (this is done using L<Import::Into>).
270 If import order is important to you, you can also pass the C<importing>
271 arguments as a flat array reference:
274 importing => [ 'PackageA', 'PackageB' ];
278 importing => [ 'PackageA' => [], 'PackageB' => [] ];
282 importing => { 'PackageA' => [], 'PackageB' => [] };
284 The import method will be called even if the list of import arguments is
285 empty or not specified,
287 If you just want to import a single package's default exports, you can
288 also pass a string instead:
290 use Package::Variant importing => 'Package';
294 An array reference of strings listing the names of subroutines that should
295 be proxied. These subroutines are expected to be installed into the new
296 variant package by the modules imported with L</importing>. Subroutines
297 with the same name will be available in your declaration package, and will
298 proxy through to the newly created package when used within
301 =head1 VARIABLE PACKAGE METHODS
303 These are methods on the variable package you declare when you import
308 Some::Variant::Package->make_variant( $target, @arguments );
310 B<You need to provide this method.> This method will be called for every
311 new variant of your package. This method should use the subroutines
312 declared in L</subs> to customize the new variant package.
314 This is a class method receiving the C<$target> package and the
315 C<@arguments> defining the requested variant.
319 use Some::Variant::Package;
320 my $variant_package = Package( @arguments );
322 This method is provided for you. It will allow a user to C<use> your
323 package and receive a subroutine taking C<@arguments> defining the variant
324 and returning the name of the newly created variant package.
326 The following options can be specified when importing:
332 use Some::Variant::Package as => 'Foo';
333 my $variant_package = Foo(@arguments);
335 Exports the generator subroutine under a different name than the default.
341 use Some::Variant::Package ();
342 my $variant_package = Some::Variant::Package->build_variant( @arguments );
344 This method is provided for you. It will generate a variant package
345 and return its name, just like the generator sub provided by
346 L</import>. This allows you to avoid importing anything into the
349 =head1 C<Package::Variant> METHODS
351 These methods are available on C<Package::Variant> itself.
353 =head2 build_variant_of
355 my $variant_package = Package::Variant
356 ->build_variant_of($variable_package, @arguments);
358 This is the dynamic method of creating new variants. It takes the
359 C<$variable_package>, which is a pre-declared variable package, and a set
360 of C<@arguments> passed to the package to generate a new
361 C<$variant_package>, which will be returned.
365 use Package::Variant @options;
367 Sets up the environment in which you declare the variants of your
368 packages. See L</OPTIONS> for details on the available options and
369 L</EXPORTS> for a list of exported subroutines.
373 Additionally to the proxies for subroutines provided in L</subs>, the
374 following exports will be available in your variable package:
378 install($method_name, $code_reference);
380 Installs a method with the given C<$method_name> into the newly created
381 variant package. The C<$code_reference> will be used as the body for the
382 method, and if L<Sub::Name> is available the coderef will be named. If you
383 want to name it something else, then use:
385 install($method_name, $name_to_use, $code_reference);
389 mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
393 phaylon - Robert Sedlacek (cpan:PHAYLON) <r.sedlacek@shadowcat.co.uk>
395 haarg - Graham Knop (cpan:HAARG) <haarg@haarg.org>
399 Copyright (c) 2010-2012 the C<Package::Variant> L</AUTHOR> and
400 L</CONTRIBUTORS> as listed above.
404 This library is free software and may be distributed under the same
405 terms as perl itself.