1Spiffy(3) User Contributed Perl Documentation Spiffy(3)
2
6 Spiffy - Spiffy Perl Interface Framework For You
7
9 package Keen;
10 use Spiffy -Base;
11 field 'mirth';
12 const mood => ':-)';
13 sub happy {
15 if ($self->mood eq ':-(') {
16 $self->mirth(-1);
17 print "Cheer up!";
18 }
19 super;
20 }
21
23 "Spiffy" is a framework and methodology for doing object oriented (OO)
24 programming in Perl. Spiffy combines the best parts of Exporter.pm,
25 base.pm, mixin.pm and SUPER.pm into one magic foundation class. It
26 attempts to fix all the nits and warts of traditional Perl OO, in a
27 clean, straightforward and (perhaps someday) standard way.
28 Spiffy borrows ideas from other OO languages like Python, Ruby, Java
30 and Perl 6. It also adds a few tricks of its own.
31 If you take a look on CPAN, there are a ton of OO related modules. When
33 starting a new project, you need to pick the set of modules that makes
34 most sense, and then you need to use those modules in each of your
35 classes. Spiffy, on the other hand, has everything you'll probably need
36 in one module, and you only need to use it once in one of your classes.
37 If you make Spiffy.pm the base class of the basest class in your
38 project, Spiffy will automatically pass all of its magic to all of your
39 subclasses. You may eventually forget that you're even using it!
40 The most striking difference between Spiffy and other Perl object ori‐
42 ented base classes, is that it has the ability to export things. If
43 you create a subclass of Spiffy, all the things that Spiffy exports
44 will automatically be exported by your subclass, in addition to any
45 more things that you want to export. And if someone creates a subclass
46 of your subclass, all of those things will be exported automatically,
47 and so on. Think of it as "Inherited Exportation", and it uses the
48 familiar Exporter.pm specification syntax.
49 To use Spiffy or any subclass of Spiffy as a base class of your class,
51 you specify the "-base" argument to the "use" command.
52 use MySpiffyBaseModule -base;
54 You can also use the traditional "use base 'MySpiffyBaseModule';" syn‐
56 tax and everything will work exactly the same. The only caveat is that
57 Spiffy.pm must already be loaded. That's because Spiffy rewires base.pm
58 on the fly to do all the Spiffy magics.
59 Spiffy has support for Ruby-like mixins with Perl6-like roles. Just
61 like "base" you can use either of the following invocations:
62 use mixin 'MySpiffyBaseModule';
64 use MySpiffyBaseModule -mixin;
65 The second version will only work if the class being mixed in is a sub‐
67 class of Spiffy. The first version will work in all cases, as long as
68 Spiffy has already been loaded.
69 To limit the methods that get mixed in, use roles. (Hint: they work
71 just like an Exporter list):
72 use MySpiffyBaseModule -mixin => qw(:basics x y !foo);
74 In object oriented Perl almost every subroutine is a method. Each
76 method gets the object passed to it as its first argument. That means
77 practically every subroutine starts with the line:
78 my $self = shift;
80 Spiffy provides a simple, optional filter mechanism to insert that line
82 for you, resulting in cleaner code. If you figure an average method has
83 10 lines of code, that's 10% of your code! To turn this option on, you
84 just use the "-Base" option instead of the "-base" option, or add the
85 "-selfless" option. If source filtering makes you queazy, don't use the
86 feature. I personally find it addictive in my quest for writing squeaky
87 clean, maintainable code.
88 A useful feature of Spiffy is that it exports two functions: "field"
90 and "const" that can be used to declare the attributes of your class,
91 and automatically generate accessor methods for them. The only differ‐
92 ence between the two functions is that "const" attributes can not be
93 modified; thus the accessor is much faster.
94 One interesting aspect of OO programming is when a method calls the
96 same method from a parent class. This is generally known as calling a
97 super method. Perl's facility for doing this is butt ugly:
98 sub cleanup {
100 my $self = shift;
101 $self->scrub;
102 $self->SUPER::cleanup(@_);
103 }
104 Spiffy makes it, er, super easy to call super methods. You just use the
106 "super" function. You don't need to pass it any arguments because it
107 automatically passes them on for you. Here's the same function with
108 Spiffy:
109 sub cleanup {
111 $self->scrub;
112 super;
113 }
114 Spiffy has a special method for parsing arguments called "parse_argu‐
116 ments", that it also uses for parsing its own arguments. You declare
117 which arguments are boolean (singletons) and which ones are paired,
118 with two special methods called "boolean_arguments" and "paired_argu‐
119 ments". Parse arguments pulls out the booleans and pairs and returns
120 them in an anonymous hash, followed by a list of the unmatched argu‐
121 ments.
122 Finally, Spiffy can export a few debugging functions "WWW", "XXX",
124 "YYY" and "ZZZ". Each of them produces a YAML dump of its arguments.
125 WWW warns the output, XXX dies with the output, YYY prints the output,
126 and ZZZ confesses the output. If YAML doesn't suit your needs, you can
127 switch all the dumps to Data::Dumper format with the "-dumper" option.
128 That's Spiffy!
130
132 Spiffy implements a completely new idea in Perl. Modules that act both
133 as object oriented classes and that also export functions. But it takes
134 the concept of Exporter.pm one step further; it walks the entire @ISA
135 path of a class and honors the export specifications of each module.
136 Since Spiffy calls on the Exporter module to do this, you can use all
137 the fancy interface features that Exporter has, including tags and
138 negation.
139 Spiffy considers all the arguments that don't begin with a dash to com‐
141 prise the export specification.
142 package Vehicle;
144 use Spiffy -base;
145 our $SERIAL_NUMBER = 0;
146 our @EXPORT = qw($SERIAL_NUMBER);
147 our @EXPORT_BASE = qw(tire horn);
148 package Bicycle;
150 use Vehicle -base, '!field';
151 $self->inflate(tire);
152 In this case, "Bicycle-"isa('Vehicle')> and also all the things that
154 "Vehicle" and "Spiffy" export, will go into "Bicycle", except "field".
155 Exporting can be very helpful when you've designed a system with hun‐
157 dreds of classes, and you want them all to have access to some func‐
158 tions or constants or variables. Just export them in your main base
159 class and every subclass will get the functions they need.
160 You can do almost everything that Exporter does because Spiffy dele‐
162 gates the job to Exporter (after adding some Spiffy magic). Spiffy
163 offers a @EXPORT_BASE variable which is like @EXPORT, but only for
164 usages that use "-base".
165
167 If you've done much OO programming in Perl you've probably used Multi‐
168 ple Inheritance (MI), and if you've done much MI you've probably run
169 into weird problems and headaches. Some languages like Ruby, attempt to
170 resolve MI issues using a technique called mixins. Basically, all Ruby
171 classes use only Single Inheritance (SI), and then mixin functionality
172 from other modules if they need to.
173 Mixins can be thought of at a simplistic level as importing the methods
175 of another class into your subclass. But from an implementation stand‐
176 point that's not the best way to do it. Spiffy does what Ruby does. It
177 creates an empty anonymous class, imports everything into that class,
178 and then chains the new class into your SI ISA path. In other words, if
179 you say:
180 package A;
182 use B -base;
183 use C -mixin;
184 use D -mixin;
185 You end up with a single inheritance chain of classes like this:
187 A << A-D << A-C << B;
189 "A-D" and "A-C" are the actual package names of the generated classes.
191 The nice thing about this style is that mixing in C doesn't clobber any
192 methods in A, and D doesn't conflict with A or C either. If you mixed
193 in a method in C that was also in A, you can still get to it by using
194 "super".
195 When Spiffy mixes in C, it pulls in all the methods in C that do not
197 begin with an underscore. Actually it goes farther than that. If C is a
198 subclass it will pull in every method that C "can" do through inheri‐
199 tance. This is very powerful, maybe too powerful.
200 To limit what you mixin, Spiffy borrows the concept of Roles from
202 Perl6. The term role is used more loosely in Spiffy though. It's much
203 like an import list that the Exporter module uses, and you can use
204 groups (tags) and negation. If the first element of your list uses
205 negation, Spiffy will start with all the methods that your mixin class
206 can do.
207 use E -mixin => qw(:tools walk !run !:sharp_tools);
209 In this example, "walk" and "run" are methods that E can do, and
211 "tools" and "sharp_tools" are roles of class E. How does class E define
212 these roles? It very simply defines methods called "_role_tools" and
213 "_role_sharp_tools" which return lists of more methods. (And possibly
214 other roles!) The neat thing here is that since roles are just methods,
215 they too can be inherited. Take that Perl6!
216
218 By using the "-Base" flag instead of "-base" you never need to write
219 the line:
220 my $self = shift;
222 This statement is added to every subroutine in your class by using a
224 source filter. The magic is simple and fast, so there is litte perfor‐
225 mance penalty for creating clean code on par with Ruby and Python.
226 package Example;
228 use Spiffy -Base;
229 sub crazy {
231 $self->nuts;
232 }
233 sub wacky { }
234 sub new() {
235 bless [], shift;
236 }
237 is exactly the same as:
239 package Example;
241 use Spiffy -base;
242 use strict;use warnings;
243 sub crazy {my $self = shift;
244 $self->nuts;
245 }
246 sub wacky {my $self = shift; }
247 sub new {
248 bless [], shift;
249 }
250 ;1;
251 Note that the empty parens after the subroutine "new" keep it from hav‐
253 ing a $self added. Also note that the extra code is added to existing
254 lines to ensure that line numbers are not altered.
255 "-Base" also turns on the strict and warnings pragmas, and adds that
257 annoying '1;' line to your module.
258
260 Spiffy now has support for private methods when you use the '-Base'
261 filter mechanism. You just declare the subs with the "my" keyword, and
262 call them with a '$' in front. Like this:
263 package Keen;
265 use SomethingSpiffy -Base;
266 # normal public method
268 sub swell {
269 $self->$stinky;
270 }
271 # private lexical method. uncallable from outside this file.
273 my sub stinky {
274 ...
275 }
276
278 The XXX function is very handy for debugging because you can insert it
279 almost anywhere, and it will dump your data in nice clean YAML. Take
280 the following statement:
281 my @stuff = grep { /keen/ } $self->find($a, $b);
283 If you have a problem with this statement, you can debug it in any of
285 the following ways:
286 XXX my @stuff = grep { /keen/ } $self->find($a, $b);
288 my @stuff = XXX grep { /keen/ } $self->find($a, $b);
289 my @stuff = grep { /keen/ } XXX $self->find($a, $b);
290 my @stuff = grep { /keen/ } $self->find(XXX $a, $b);
291 XXX is easy to insert and remove. It is also a tradition to mark uncer‐
293 tain areas of code with XXX. This will make the debugging dumpers easy
294 to spot if you forget to take them out.
295 WWW and YYY are nice because they dump their arguments and then return
297 the arguments. This way you can insert them into many places and still
298 have the code run as before. Use ZZZ when you need to die with both a
299 YAML dump and a full stack trace.
300 The debugging functions are exported by default if you use the "-base"
302 option, but only if you have previously used the "-XXX" option. To
303 export all 4 functions use the export tag:
304 use SomeSpiffyModule ':XXX';
306 To force the debugging functions to use Data::Dumper instead of YAML:
308 use SomeSpiffyModule -dumper;
310
312 This section describes the functions the Spiffy exports. The "field",
313 "const", "stub" and "super" functions are only exported when you use
314 the "-base" or "-Base" options.
315 * field
317 Defines accessor methods for a field of your class:
318 package Example;
320 use Spiffy -Base;
321 field 'foo';
323 field bar => [];
324 sub lalala {
326 $self->foo(42);
327 push @{$self->{bar}}, $self->foo;
328 }
329 The first parameter passed to "field" is the name of the attribute
331 being defined. Accessors can be given an optional default value.
332 This value will be returned if no value for the field has been set
333 in the object.
334 * const
336 const bar => 42;
337 The "const" function is similar to <field> except that it is
339 immutable. It also does not store data in the object. You probably
340 always want to give a "const" a default value, otherwise the gener‐
341 ated method will be somewhat useless.
342 * stub
344 stub 'cigar';
345 The "stub" function generates a method that will die with an appro‐
347 priate message. The idea is that subclasses must implement these
348 methods so that the stub methods don't get called.
349 * super
351 If this function is called without any arguments, it will call the
352 same method that it is in, higher up in the ISA tree, passing it
353 all the same arguments. If it is called with arguments, it will use
354 those arguments with $self in the front. In other words, it just
355 works like you'd expect.
356 sub foo {
358 super; # Same as $self->SUPER::foo(@_);
359 super('hello'); # Same as $self->SUPER::foo('hello');
360 $self->bar(42);
361 }
362 sub new() {
364 my $self = super;
365 $self->init;
366 return $self;
367 }
368 "super" will simply do nothing if there is no super method.
370 Finally, "super" does the right thing in AUTOLOAD subroutines.
371
373 This section lists all of the methods that any subclass of Spiffy auto‐
374 matically inherits.
375 * mixin
377 A method to mixin a class at runtime. Takes the same arguments as
378 "use mixin ...". Makes the target class a mixin of the caller.
379 $self->mixin('SomeClass');
381 $object->mixin('SomeOtherClass' => 'some_method');
382 * parse_arguments
384 This method takes a list of arguments and groups them into pairs.
385 It allows for boolean arguments which may or may not have a value
386 (defaulting to 1). The method returns a hash reference of all the
387 pairs as keys and values in the hash. Any arguments that cannot be
388 paired, are returned as a list. Here is an example:
389 sub boolean_arguments { qw(-has_spots -is_yummy) }
391 sub paired_arguments { qw(-name -size) }
392 my ($pairs, @others) = $self->parse_arguments(
393 'red', 'white',
394 -name => 'Ingy',
395 -has_spots =>
396 -size => 'large',
397 'black',
398 -is_yummy => 0,
399 );
400 After this call, $pairs will contain:
402 {
404 -name => 'Ingy',
405 -has_spots => 1,
406 -size => 'large',
407 -is_yummy => 0,
408 }
409 and @others will contain 'red', 'white', and 'black'.
411 * boolean_arguments
413 Returns the list of arguments that are recognized as being boolean.
414 Override this method to define your own list.
415 * paired_arguments
417 Returns the list of arguments that are recognized as being paired.
418 Override this method to define your own list.
419
421 When you "use" the Spiffy module or a subclass of it, you can pass it a
422 list of arguments. These arguments are parsed using the "parse_argu‐
423 ments" method described above. The special argument "-base", is used to
424 make the current package a subclass of the Spiffy module being used.
425 Any non-paired parameters act like a normal import list; just like
427 those used with the Exporter module.
428
430 The proper way to use a Spiffy module as a base class is with the
431 "-base" parameter to the "use" statement. This differs from typical
432 modules where you would want to "use base".
433 package Something;
435 use Spiffy::Module -base;
436 use base 'NonSpiffy::Module';
437 Now it may be hard to keep track of what's Spiffy and what is not.
439 Therefore Spiffy has actually been made to work with base.pm. You can
440 say:
441 package Something;
443 use base 'Spiffy::Module';
444 use base 'NonSpiffy::Module';
445 "use base" is also very useful when your class is not an actual module
447 (a separate file) but just a package in some file that has already been
448 loaded. "base" will work whether the class is a module or not, while
449 the "-base" syntax cannot work that way, since "use" always tries to
450 load a module.
451 base.pm Caveats
453 To make Spiffy work with base.pm, a dirty trick was played. Spiffy
455 swaps "base::import" with its own version. If the base modules are not
456 Spiffy, Spiffy calls the original base::import. If the base modules are
457 Spiffy, then Spiffy does its own thing.
458 There are two caveats.
460 * Spiffy must be loaded first.
462 If Spiffy is not loaded and "use base" is invoked on a Spiffy mod‐
463 ule, Spiffy will die with a useful message telling the author to
464 read this documentation. That's because Spiffy needed to do the
465 import swap beforehand.
466 If you get this error, simply put a statement like this up front in
468 your code:
469 use Spiffy ();
471 * No Mixing
473 "base.pm" can take multiple arguments. And this works with Spiffy
474 as long as all the base classes are Spiffy, or they are all
475 non-Spiffy. If they are mixed, Spiffy will die. In this case just
476 use separate "use base" statements.
477
479 Spiffy is a wonderful way to do OO programming in Perl, but it is still
480 a work in progress. New things will be added, and things that don't
481 work well, might be removed.
482
484 Ingy döt Net <ingy@cpan.org>
485
487 Copyright (c) 2006. Ingy döt Net. All rights reserved. Copyright (c)
488 2004. Brian Ingerson. All rights reserved.
489 This program is free software; you can redistribute it and/or modify it
491 under the same terms as Perl itself.
492 See <http://www.perl.com/perl/misc/Artistic.html>
494perl v5.8.8 2006-01-29 Spiffy(3)