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);
56 # Determine parameter list structure, one of:
57 # struct( class => [ element-list ])
58 # struct( class => { element-list })
59 # struct( element-list )
60 # Latter form assumes current package name as struct name.
63 my $base_type = ref $_[1];
64 if ( $base_type eq 'HASH' ) {
69 elsif ( $base_type eq 'ARRAY' ) {
76 $class = (caller())[0];
79 _usage_error() if @decls % 2 == 1;
81 # Ensure we are not, and will not be, a subclass.
87 _subclass_error() if @$isa;
88 tie @$isa, 'Class::Struct::Tie_ISA';
92 croak "function 'new' already defined in package $class"
93 if do { no strict 'refs'; defined &{$class . "::new"} };
103 $out = "{\n package $class;\n use Carp;\n sub new {\n";
104 $out .= " my (\$class, \%init) = \@_;\n";
105 $out .= " \$class = __PACKAGE__ unless \@_;\n";
109 my( $cmt, $name, $type, $elem );
111 if( $base_type eq 'HASH' ){
112 $out .= " my(\$r) = {};\n";
115 elsif( $base_type eq 'ARRAY' ){
116 $out .= " my(\$r) = [];\n";
118 while( $idx < @decls ){
119 $name = $decls[$idx];
120 $type = $decls[$idx+1];
121 push( @methods, $name );
122 if( $base_type eq 'HASH' ){
123 $elem = "{'${class}::$name'}";
125 elsif( $base_type eq 'ARRAY' ){
130 if( $type =~ /^\*(.)/ ){
134 my $init = "defined(\$init{'$name'}) ? \$init{'$name'} :";
136 $out .= " croak 'Initializer for $name must be array reference'\n";
137 $out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'ARRAY';\n";
138 $out .= " \$r->$elem = $init [];$cmt\n";
141 elsif( $type eq '%' ){
142 $out .= " croak 'Initializer for $name must be hash reference'\n";
143 $out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'HASH';\n";
144 $out .= " \$r->$elem = $init {};$cmt\n";
147 elsif ( $type eq '$') {
148 $out .= " \$r->$elem = $init undef;$cmt\n";
150 elsif( $type =~ /^\w+(?:::\w+)*$/ ){
151 $init = "defined(\$init{'$name'}) ? \%{\$init{'$name'}} : ()";
152 $out .= " croak 'Initializer for $name must be hash reference'\n";
153 $out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'HASH';\n";
154 $out .= " \$r->$elem = '${type}'->new($init);$cmt\n";
155 $classes{$name} = $type;
159 croak "'$type' is not a valid struct element type";
163 $out .= " bless \$r, \$class;\n }\n";
165 # Create accessor methods.
167 my( $pre, $pst, $sel );
169 foreach $name (@methods){
170 if ( do { no strict 'refs'; defined &{$class . "::$name"} } ) {
171 warnings::warn "function '$name' already defined, overrides struct accessor method"
172 if warnings::enabled();
175 $pre = $pst = $cmt = $sel = '';
176 if( defined $refs{$name} ){
179 $cmt = " # returns ref";
181 $out .= " sub $name {$cmt\n my \$r = shift;\n";
182 if( $base_type eq 'ARRAY' ){
186 elsif( $base_type eq 'HASH' ){
187 $elem = "{'${class}::$name'}";
189 if( defined $arrays{$name} ){
190 $out .= " my \$i;\n";
191 $out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n";
194 elsif( defined $hashes{$name} ){
195 $out .= " my \$i;\n";
196 $out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n";
199 elsif( defined $classes{$name} ){
200 if ( $CHECK_CLASS_MEMBERSHIP ) {
201 $out .= " croak '$name argument is wrong class' if \@_ && ! UNIVERSAL::isa(\$_[0], '$classes{$name}');\n";
204 $out .= " croak 'Too many args to $name' if \@_ > 1;\n";
205 $out .= " \@_ ? ($pre\$r->$elem$sel = shift$pst) : $pre\$r->$elem$sel$pst;\n";
211 print $out if $print;
212 my $result = eval $out;
217 confess "struct usage error";
220 sub _subclass_error {
221 croak 'struct class cannot be a subclass (@ISA not allowed)';
231 Class::Struct - declare struct-like datatypes as Perl classes
236 # declare struct, based on array:
237 struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]);
238 # declare struct, based on hash:
239 struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... });
243 # declare struct, based on array, implicit class name:
244 struct( ELEMENT_NAME => ELEMENT_TYPE, ... );
249 # declare struct with four types of elements:
250 struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' );
252 $obj = new Myobj; # constructor
254 # scalar type accessor:
255 $element_value = $obj->s; # element value
256 $obj->s('new value'); # assign to element
258 # array type accessor:
259 $ary_ref = $obj->a; # reference to whole array
260 $ary_element_value = $obj->a(2); # array element value
261 $obj->a(2, 'new value'); # assign to array element
263 # hash type accessor:
264 $hash_ref = $obj->h; # reference to whole hash
265 $hash_element_value = $obj->h('x'); # hash element value
266 $obj->h('x', 'new value'); # assign to hash element
268 # class type accessor:
269 $element_value = $obj->c; # object reference
270 $obj->c->method(...); # call method of object
271 $obj->c(new My_Other_Class); # assign a new object
276 C<Class::Struct> exports a single function, C<struct>.
277 Given a list of element names and types, and optionally
278 a class name, C<struct> creates a Perl 5 class that implements
279 a "struct-like" data structure.
281 The new class is given a constructor method, C<new>, for creating
284 Each element in the struct data has an accessor method, which is
285 used to assign to the element and to fetch its value. The
286 default accessor can be overridden by declaring a C<sub> of the
287 same name in the package. (See Example 2.)
289 Each element's type can be scalar, array, hash, or class.
292 =head2 The C<struct()> function
294 The C<struct> function has three forms of parameter-list.
296 struct( CLASS_NAME => [ ELEMENT_LIST ]);
297 struct( CLASS_NAME => { ELEMENT_LIST });
298 struct( ELEMENT_LIST );
300 The first and second forms explicitly identify the name of the
301 class being created. The third form assumes the current package
302 name as the class name.
304 An object of a class created by the first and third forms is
305 based on an array, whereas an object of a class created by the
306 second form is based on a hash. The array-based forms will be
307 somewhat faster and smaller; the hash-based forms are more
310 The class created by C<struct> must not be a subclass of another
311 class other than C<UNIVERSAL>.
313 It can, however, be used as a superclass for other classes. To facilitate
314 this, the generated constructor method uses a two-argument blessing.
315 Furthermore, if the class is hash-based, the key of each element is
316 prefixed with the class name (see I<Perl Cookbook>, Recipe 13.12).
318 A function named C<new> must not be explicitly defined in a class
319 created by C<struct>.
321 The I<ELEMENT_LIST> has the form
325 Each name-type pair declares one element of the struct. Each
326 element name will be defined as an accessor method unless a
327 method by that name is explicitly defined; in the latter case, a
328 warning is issued if the warning flag (B<-w>) is set.
331 =head2 Element Types and Accessor Methods
333 The four element types -- scalar, array, hash, and class -- are
334 represented by strings -- C<'$'>, C<'@'>, C<'%'>, and a class name --
335 optionally preceded by a C<'*'>.
337 The accessor method provided by C<struct> for an element depends
338 on the declared type of the element.
342 =item Scalar (C<'$'> or C<'*$'>)
344 The element is a scalar, and by default is initialized to C<undef>
345 (but see L<Initializing with new>).
347 The accessor's argument, if any, is assigned to the element.
349 If the element type is C<'$'>, the value of the element (after
350 assignment) is returned. If the element type is C<'*$'>, a reference
351 to the element is returned.
353 =item Array (C<'@'> or C<'*@'>)
355 The element is an array, initialized by default to C<()>.
357 With no argument, the accessor returns a reference to the
358 element's whole array (whether or not the element was
359 specified as C<'@'> or C<'*@'>).
361 With one or two arguments, the first argument is an index
362 specifying one element of the array; the second argument, if
363 present, is assigned to the array element. If the element type
364 is C<'@'>, the accessor returns the array element value. If the
365 element type is C<'*@'>, a reference to the array element is
368 =item Hash (C<'%'> or C<'*%'>)
370 The element is a hash, initialized by default to C<()>.
372 With no argument, the accessor returns a reference to the
373 element's whole hash (whether or not the element was
374 specified as C<'%'> or C<'*%'>).
376 With one or two arguments, the first argument is a key specifying
377 one element of the hash; the second argument, if present, is
378 assigned to the hash element. If the element type is C<'%'>, the
379 accessor returns the hash element value. If the element type is
380 C<'*%'>, a reference to the hash element is returned.
382 =item Class (C<'Class_Name'> or C<'*Class_Name'>)
384 The element's value must be a reference blessed to the named
385 class or to one of its subclasses. The element is initialized to
386 the result of calling the C<new> constructor of the named class.
388 The accessor's argument, if any, is assigned to the element. The
389 accessor will C<croak> if this is not an appropriate object
392 If the element type does not start with a C<'*'>, the accessor
393 returns the element value (after assignment). If the element type
394 starts with a C<'*'>, a reference to the element itself is returned.
398 =head2 Initializing with C<new>
400 C<struct> always creates a constructor called C<new>. That constructor
401 may take a list of initializers for the various elements of the new
404 Each initializer is a pair of values: I<element name>C< =E<gt> >I<value>.
405 The initializer value for a scalar element is just a scalar value. The
406 initializer for an array element is an array reference. The initializer
407 for a hash is a hash reference.
409 The initializer for a class element is also a hash reference, and the
410 contents of that hash are passed to the element's own constructor.
412 See Example 3 below for an example of initialization.
421 Giving a struct element a class type that is also a struct is how
422 structs are nested. Here, C<timeval> represents a time (seconds and
423 microseconds), and C<rusage> has two elements, each of which is of
429 ru_utime => timeval, # seconds
430 ru_stime => timeval, # microseconds
441 # $t->ru_utime and $t->ru_stime are objects of type timeval.
442 # set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec.
443 $t->ru_utime->tv_secs(100);
444 $t->ru_utime->tv_usecs(0);
445 $t->ru_stime->tv_secs(5);
446 $t->ru_stime->tv_usecs(0);
451 An accessor function can be redefined in order to provide
452 additional checking of values, etc. Here, we want the C<count>
453 element always to be nonnegative, so we redefine the C<count>
454 accessor accordingly.
460 struct ( 'MyObj', { count => '$', stuff => '%' } );
462 # override the default accessor method for 'count'
466 die 'count must be nonnegative' if $_[0] < 0;
467 $self->{'count'} = shift;
468 warn "Too many args to count" if @_;
470 return $self->{'count'};
475 print "\$x->count(5) = ", $x->count(5), "\n";
476 # prints '$x->count(5) = 5'
478 print "\$x->count = ", $x->count, "\n";
479 # prints '$x->count = 5'
481 print "\$x->count(-5) = ", $x->count(-5), "\n";
482 # dies due to negative argument!
486 The constructor of a generated class can be passed a list
487 of I<element>=>I<value> pairs, with which to initialize the struct.
488 If no initializer is specified for a particular element, its default
489 initialization is performed instead. Initializers for non-existent
490 elements are silently ignored.
492 Note that the initializer for a nested struct is specified
493 as an anonymous hash of initializers, which is passed on to the nested
494 struct's constructor.
514 my $cat = Cat->new( name => 'Socks',
515 kittens => ['Monica', 'Kenneth'],
516 markings => { socks=>1, blaze=>"white" },
517 breed => { name=>'short-hair', cross=>1 },
520 print "Once a cat called ", $cat->name, "\n";
521 print "(which was a ", $cat->breed->name, ")\n";
522 print "had two kittens: ", join(' and ', @{$cat->kittens}), "\n";
526 =head1 Author and Modification History
529 Modified by Damian Conway, 1999-03-05, v0.58.
531 Added handling of hash-like arg list to class ctor.
533 Changed to two-argument blessing in ctor to support
534 derivation from created classes.
536 Added classname prefixes to keys in hash-based classes
537 (refer to "Perl Cookbook", Recipe 13.12 for rationale).
539 Corrected behaviour of accessors for '*@' and '*%' struct
540 elements. Package now implements documented behaviour when
541 returning a reference to an entire hash or array element.
542 Previously these were returned as a reference to a reference
546 Renamed to C<Class::Struct> and modified by Jim Miner, 1997-04-02.
548 members() function removed.
549 Documentation corrected and extended.
550 Use of struct() in a subclass prohibited.
551 User definition of accessor allowed.
552 Treatment of '*' in element types corrected.
553 Treatment of classes as element types corrected.
554 Class name to struct() made optional.
555 Diagnostic checks added.
558 Originally C<Class::Template> by Dean Roehrich.
560 # Template.pm --- struct/member template builder
564 # changes/bugs fixed since 28nov94 version:
566 # changes/bugs fixed since 21nov94 version:
568 # changes/bugs fixed since 02sep94 version:
569 # - Moved to Class::Template.
570 # changes/bugs fixed since 20feb94 version:
571 # - Updated to be a more proper module.
572 # - Added "use strict".
573 # - Bug in build_methods, was using @var when @$var needed.
574 # - Now using my() rather than local().
576 # Uses perl5 classes to create nested data types.
577 # This is offered as one implementation of Tom Christiansen's "structs.pl"