3 ## See POD after __END__
8 use warnings::register;
9 our(@ISA, @EXPORT, $VERSION);
19 ## Tested on 5.002 and 5.003 without class membership tests:
20 my $CHECK_CLASS_MEMBERSHIP = ($] >= 5.003_95);
24 if (@_) { $print = shift }
29 package Class::Struct::Tie_ISA;
33 return bless [], $class;
37 my ($self, $index, $value) = @_;
38 Class::Struct::_subclass_error();
42 my ($self, $index) = @_;
48 return scalar(@$self);
60 $self->export_to_level( 1, $self, @EXPORT );
66 # Determine parameter list structure, one of:
67 # struct( class => [ element-list ])
68 # struct( class => { element-list })
69 # struct( element-list )
70 # Latter form assumes current package name as struct name.
73 my $base_type = ref $_[1];
74 if ( $base_type eq 'HASH' ) {
79 elsif ( $base_type eq 'ARRAY' ) {
86 $class = (caller())[0];
90 _usage_error() if @decls % 2 == 1;
92 # Ensure we are not, and will not be, a subclass.
98 _subclass_error() if @$isa;
99 tie @$isa, 'Class::Struct::Tie_ISA';
101 # Create constructor.
103 croak "function 'new' already defined in package $class"
104 if do { no strict 'refs'; defined &{$class . "::new"} };
114 $out = "{\n package $class;\n use Carp;\n sub new {\n";
115 $out .= " my (\$class, \%init) = \@_;\n";
116 $out .= " \$class = __PACKAGE__ unless \@_;\n";
120 my( $cmt, $name, $type, $elem );
122 if( $base_type eq 'HASH' ){
123 $out .= " my(\$r) = {};\n";
126 elsif( $base_type eq 'ARRAY' ){
127 $out .= " my(\$r) = [];\n";
129 while( $idx < @decls ){
130 $name = $decls[$idx];
131 $type = $decls[$idx+1];
132 push( @methods, $name );
133 if( $base_type eq 'HASH' ){
134 $elem = "{'${class}::$name'}";
136 elsif( $base_type eq 'ARRAY' ){
141 if( $type =~ /^\*(.)/ ){
145 my $init = "defined(\$init{'$name'}) ? \$init{'$name'} :";
147 $out .= " croak 'Initializer for $name must be array reference'\n";
148 $out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'ARRAY';\n";
149 $out .= " \$r->$elem = $init [];$cmt\n";
152 elsif( $type eq '%' ){
153 $out .= " croak 'Initializer for $name must be hash reference'\n";
154 $out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'HASH';\n";
155 $out .= " \$r->$elem = $init {};$cmt\n";
158 elsif ( $type eq '$') {
159 $out .= " \$r->$elem = $init undef;$cmt\n";
161 elsif( $type =~ /^\w+(?:::\w+)*$/ ){
162 $init = "defined(\$init{'$name'}) ? \%{\$init{'$name'}} : ()";
163 $out .= " croak 'Initializer for $name must be hash reference'\n";
164 $out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'HASH';\n";
165 $out .= " \$r->$elem = '${type}'->new($init);$cmt\n";
166 $classes{$name} = $type;
170 croak "'$type' is not a valid struct element type";
174 $out .= " bless \$r, \$class;\n }\n";
176 # Create accessor methods.
178 my( $pre, $pst, $sel );
180 foreach $name (@methods){
181 if ( do { no strict 'refs'; defined &{$class . "::$name"} } ) {
182 warnings::warnif("function '$name' already defined, overrides struct accessor method");
185 $pre = $pst = $cmt = $sel = '';
186 if( defined $refs{$name} ){
189 $cmt = " # returns ref";
191 $out .= " sub $name {$cmt\n my \$r = shift;\n";
192 if( $base_type eq 'ARRAY' ){
196 elsif( $base_type eq 'HASH' ){
197 $elem = "{'${class}::$name'}";
199 if( defined $arrays{$name} ){
200 $out .= " my \$i;\n";
201 $out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n";
204 elsif( defined $hashes{$name} ){
205 $out .= " my \$i;\n";
206 $out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n";
209 elsif( defined $classes{$name} ){
210 if ( $CHECK_CLASS_MEMBERSHIP ) {
211 $out .= " croak '$name argument is wrong class' if \@_ && ! UNIVERSAL::isa(\$_[0], '$classes{$name}');\n";
214 $out .= " croak 'Too many args to $name' if \@_ > 1;\n";
215 $out .= " \@_ ? ($pre\$r->$elem$sel = shift$pst) : $pre\$r->$elem$sel$pst;\n";
221 print $out if $print;
222 my $result = eval $out;
227 confess "struct usage error";
230 sub _subclass_error {
231 croak 'struct class cannot be a subclass (@ISA not allowed)';
241 Class::Struct - declare struct-like datatypes as Perl classes
246 # declare struct, based on array:
247 struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]);
248 # declare struct, based on hash:
249 struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... });
253 # declare struct, based on array, implicit class name:
254 struct( ELEMENT_NAME => ELEMENT_TYPE, ... );
256 # Declare struct at compile time
257 use Class::Struct CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ];
258 use Class::Struct CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... };
262 # declare struct with four types of elements:
263 struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' );
265 $obj = new Myobj; # constructor
267 # scalar type accessor:
268 $element_value = $obj->s; # element value
269 $obj->s('new value'); # assign to element
271 # array type accessor:
272 $ary_ref = $obj->a; # reference to whole array
273 $ary_element_value = $obj->a(2); # array element value
274 $obj->a(2, 'new value'); # assign to array element
276 # hash type accessor:
277 $hash_ref = $obj->h; # reference to whole hash
278 $hash_element_value = $obj->h('x'); # hash element value
279 $obj->h('x', 'new value'); # assign to hash element
281 # class type accessor:
282 $element_value = $obj->c; # object reference
283 $obj->c->method(...); # call method of object
284 $obj->c(new My_Other_Class); # assign a new object
288 C<Class::Struct> exports a single function, C<struct>.
289 Given a list of element names and types, and optionally
290 a class name, C<struct> creates a Perl 5 class that implements
291 a "struct-like" data structure.
293 The new class is given a constructor method, C<new>, for creating
296 Each element in the struct data has an accessor method, which is
297 used to assign to the element and to fetch its value. The
298 default accessor can be overridden by declaring a C<sub> of the
299 same name in the package. (See Example 2.)
301 Each element's type can be scalar, array, hash, or class.
303 =head2 The C<struct()> function
305 The C<struct> function has three forms of parameter-list.
307 struct( CLASS_NAME => [ ELEMENT_LIST ]);
308 struct( CLASS_NAME => { ELEMENT_LIST });
309 struct( ELEMENT_LIST );
311 The first and second forms explicitly identify the name of the
312 class being created. The third form assumes the current package
313 name as the class name.
315 An object of a class created by the first and third forms is
316 based on an array, whereas an object of a class created by the
317 second form is based on a hash. The array-based forms will be
318 somewhat faster and smaller; the hash-based forms are more
321 The class created by C<struct> must not be a subclass of another
322 class other than C<UNIVERSAL>.
324 It can, however, be used as a superclass for other classes. To facilitate
325 this, the generated constructor method uses a two-argument blessing.
326 Furthermore, if the class is hash-based, the key of each element is
327 prefixed with the class name (see I<Perl Cookbook>, Recipe 13.12).
329 A function named C<new> must not be explicitly defined in a class
330 created by C<struct>.
332 The I<ELEMENT_LIST> has the form
336 Each name-type pair declares one element of the struct. Each
337 element name will be defined as an accessor method unless a
338 method by that name is explicitly defined; in the latter case, a
339 warning is issued if the warning flag (B<-w>) is set.
341 =head2 Class Creation at Compile Time
343 C<Class::Struct> can create your class at compile time. The main reason
344 for doing this is obvious, so your class acts like every other class in
345 Perl. Creating your class at compile time will make the order of events
346 similar to using any other class ( or Perl module ).
348 There is no significant speed gain between compile time and run time
349 class creation, there is just a new, more standard order of events.
351 =head2 Element Types and Accessor Methods
353 The four element types -- scalar, array, hash, and class -- are
354 represented by strings -- C<'$'>, C<'@'>, C<'%'>, and a class name --
355 optionally preceded by a C<'*'>.
357 The accessor method provided by C<struct> for an element depends
358 on the declared type of the element.
362 =item Scalar (C<'$'> or C<'*$'>)
364 The element is a scalar, and by default is initialized to C<undef>
365 (but see L<Initializing with new>).
367 The accessor's argument, if any, is assigned to the element.
369 If the element type is C<'$'>, the value of the element (after
370 assignment) is returned. If the element type is C<'*$'>, a reference
371 to the element is returned.
373 =item Array (C<'@'> or C<'*@'>)
375 The element is an array, initialized by default to C<()>.
377 With no argument, the accessor returns a reference to the
378 element's whole array (whether or not the element was
379 specified as C<'@'> or C<'*@'>).
381 With one or two arguments, the first argument is an index
382 specifying one element of the array; the second argument, if
383 present, is assigned to the array element. If the element type
384 is C<'@'>, the accessor returns the array element value. If the
385 element type is C<'*@'>, a reference to the array element is
388 =item Hash (C<'%'> or C<'*%'>)
390 The element is a hash, initialized by default to C<()>.
392 With no argument, the accessor returns a reference to the
393 element's whole hash (whether or not the element was
394 specified as C<'%'> or C<'*%'>).
396 With one or two arguments, the first argument is a key specifying
397 one element of the hash; the second argument, if present, is
398 assigned to the hash element. If the element type is C<'%'>, the
399 accessor returns the hash element value. If the element type is
400 C<'*%'>, a reference to the hash element is returned.
402 =item Class (C<'Class_Name'> or C<'*Class_Name'>)
404 The element's value must be a reference blessed to the named
405 class or to one of its subclasses. The element is initialized to
406 the result of calling the C<new> constructor of the named class.
408 The accessor's argument, if any, is assigned to the element. The
409 accessor will C<croak> if this is not an appropriate object
412 If the element type does not start with a C<'*'>, the accessor
413 returns the element value (after assignment). If the element type
414 starts with a C<'*'>, a reference to the element itself is returned.
418 =head2 Initializing with C<new>
420 C<struct> always creates a constructor called C<new>. That constructor
421 may take a list of initializers for the various elements of the new
424 Each initializer is a pair of values: I<element name>C< =E<gt> >I<value>.
425 The initializer value for a scalar element is just a scalar value. The
426 initializer for an array element is an array reference. The initializer
427 for a hash is a hash reference.
429 The initializer for a class element is also a hash reference, and the
430 contents of that hash are passed to the element's own constructor.
432 See Example 3 below for an example of initialization.
440 Giving a struct element a class type that is also a struct is how
441 structs are nested. Here, C<timeval> represents a time (seconds and
442 microseconds), and C<rusage> has two elements, each of which is of
448 ru_utime => timeval, # seconds
449 ru_stime => timeval, # microseconds
460 # $t->ru_utime and $t->ru_stime are objects of type timeval.
461 # set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec.
462 $t->ru_utime->tv_secs(100);
463 $t->ru_utime->tv_usecs(0);
464 $t->ru_stime->tv_secs(5);
465 $t->ru_stime->tv_usecs(0);
469 An accessor function can be redefined in order to provide
470 additional checking of values, etc. Here, we want the C<count>
471 element always to be nonnegative, so we redefine the C<count>
472 accessor accordingly.
478 struct ( 'MyObj', { count => '$', stuff => '%' } );
480 # override the default accessor method for 'count'
484 die 'count must be nonnegative' if $_[0] < 0;
485 $self->{'count'} = shift;
486 warn "Too many args to count" if @_;
488 return $self->{'count'};
493 print "\$x->count(5) = ", $x->count(5), "\n";
494 # prints '$x->count(5) = 5'
496 print "\$x->count = ", $x->count, "\n";
497 # prints '$x->count = 5'
499 print "\$x->count(-5) = ", $x->count(-5), "\n";
500 # dies due to negative argument!
504 The constructor of a generated class can be passed a list
505 of I<element>=>I<value> pairs, with which to initialize the struct.
506 If no initializer is specified for a particular element, its default
507 initialization is performed instead. Initializers for non-existent
508 elements are silently ignored.
510 Note that the initializer for a nested struct is specified
511 as an anonymous hash of initializers, which is passed on to the nested
512 struct's constructor.
531 my $cat = Cat->new( name => 'Socks',
532 kittens => ['Monica', 'Kenneth'],
533 markings => { socks=>1, blaze=>"white" },
534 breed => { name=>'short-hair', cross=>1 },
537 print "Once a cat called ", $cat->name, "\n";
538 print "(which was a ", $cat->breed->name, ")\n";
539 print "had two kittens: ", join(' and ', @{$cat->kittens}), "\n";
543 =head1 Author and Modification History
545 Modified by Casey Tweten, 2000-11-08, v0.59.
547 Added the ability for compile time class creation.
549 Modified by Damian Conway, 1999-03-05, v0.58.
551 Added handling of hash-like arg list to class ctor.
553 Changed to two-argument blessing in ctor to support
554 derivation from created classes.
556 Added classname prefixes to keys in hash-based classes
557 (refer to "Perl Cookbook", Recipe 13.12 for rationale).
559 Corrected behaviour of accessors for '*@' and '*%' struct
560 elements. Package now implements documented behaviour when
561 returning a reference to an entire hash or array element.
562 Previously these were returned as a reference to a reference
565 Renamed to C<Class::Struct> and modified by Jim Miner, 1997-04-02.
567 members() function removed.
568 Documentation corrected and extended.
569 Use of struct() in a subclass prohibited.
570 User definition of accessor allowed.
571 Treatment of '*' in element types corrected.
572 Treatment of classes as element types corrected.
573 Class name to struct() made optional.
574 Diagnostic checks added.
576 Originally C<Class::Template> by Dean Roehrich.
578 # Template.pm --- struct/member template builder
582 # changes/bugs fixed since 28nov94 version:
584 # changes/bugs fixed since 21nov94 version:
586 # changes/bugs fixed since 02sep94 version:
587 # - Moved to Class::Template.
588 # changes/bugs fixed since 20feb94 version:
589 # - Updated to be a more proper module.
590 # - Added "use strict".
591 # - Bug in build_methods, was using @var when @$var needed.
592 # - Now using my() rather than local().
594 # Uses perl5 classes to create nested data types.
595 # This is offered as one implementation of Tom Christiansen's "structs.pl"