3 ## See POD after __END__
8 use vars qw(@ISA @EXPORT $VERSION);
18 ## Tested on 5.002 and 5.003 without class membership tests:
19 my $CHECK_CLASS_MEMBERSHIP = ($] >= 5.003_95);
23 if (@_) { $print = shift }
28 package Class::Struct::Tie_ISA;
32 return bless [], $class;
36 my ($self, $index, $value) = @_;
37 Class::Struct::_subclass_error();
41 my ($self, $index) = @_;
47 return scalar(@$self);
55 # Determine parameter list structure, one of:
56 # struct( class => [ element-list ])
57 # struct( class => { element-list })
58 # struct( element-list )
59 # Latter form assumes current package name as struct name.
62 my $base_type = ref $_[1];
63 if ( $base_type eq 'HASH' ) {
68 elsif ( $base_type eq 'ARRAY' ) {
75 $class = (caller())[0];
78 _usage_error() if @decls % 2 == 1;
80 # Ensure we are not, and will not be, a subclass.
86 _subclass_error() if @$isa;
87 tie @$isa, 'Class::Struct::Tie_ISA';
91 croak "function 'new' already defined in package $class"
92 if do { no strict 'refs'; defined &{$class . "::new"} };
102 $out = "{\n package $class;\n use Carp;\n sub new {\n";
103 $out .= " my (\$class, \%init) = \@_;\n";
107 my( $cmt, $name, $type, $elem );
109 if( $base_type eq 'HASH' ){
110 $out .= " my(\$r) = {};\n";
113 elsif( $base_type eq 'ARRAY' ){
114 $out .= " my(\$r) = [];\n";
116 while( $idx < @decls ){
117 $name = $decls[$idx];
118 $type = $decls[$idx+1];
119 push( @methods, $name );
120 if( $base_type eq 'HASH' ){
121 $elem = "{'${class}::$name'}";
123 elsif( $base_type eq 'ARRAY' ){
128 if( $type =~ /^\*(.)/ ){
132 my $init = "defined(\$init{'$name'}) ? \$init{'$name'} :";
134 $out .= " croak 'Initializer for $name must be array reference'\n";
135 $out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'ARRAY';\n";
136 $out .= " \$r->$elem = $init [];$cmt\n";
139 elsif( $type eq '%' ){
140 $out .= " croak 'Initializer for $name must be hash reference'\n";
141 $out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'HASH';\n";
142 $out .= " \$r->$elem = $init {};$cmt\n";
145 elsif ( $type eq '$') {
146 $out .= " \$r->$elem = $init undef;$cmt\n";
148 elsif( $type =~ /^\w+(?:::\w+)*$/ ){
149 $init = "defined(\$init{'$name'}) ? \%{\$init{'$name'}} : ()";
150 $out .= " croak 'Initializer for $name must be hash reference'\n";
151 $out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'HASH';\n";
152 $out .= " \$r->$elem = '${type}'->new($init);$cmt\n";
153 $classes{$name} = $type;
157 croak "'$type' is not a valid struct element type";
161 $out .= " bless \$r, \$class;\n }\n";
163 # Create accessor methods.
165 my( $pre, $pst, $sel );
167 foreach $name (@methods){
168 if ( do { no strict 'refs'; defined &{$class . "::$name"} } ) {
169 carp "function '$name' already defined, overrides struct accessor method"
173 $pre = $pst = $cmt = $sel = '';
174 if( defined $refs{$name} ){
177 $cmt = " # returns ref";
179 $out .= " sub $name {$cmt\n my \$r = shift;\n";
180 if( $base_type eq 'ARRAY' ){
184 elsif( $base_type eq 'HASH' ){
185 $elem = "{'${class}::$name'}";
187 if( defined $arrays{$name} ){
188 $out .= " my \$i;\n";
189 $out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n";
192 elsif( defined $hashes{$name} ){
193 $out .= " my \$i;\n";
194 $out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n";
197 elsif( defined $classes{$name} ){
198 if ( $CHECK_CLASS_MEMBERSHIP ) {
199 $out .= " croak '$name argument is wrong class' if \@_ && ! UNIVERSAL::isa(\$_[0], '$classes{$name}');\n";
202 $out .= " croak 'Too many args to $name' if \@_ > 1;\n";
203 $out .= " \@_ ? ($pre\$r->$elem$sel = shift$pst) : $pre\$r->$elem$sel$pst;\n";
209 print $out if $print;
210 my $result = eval $out;
215 confess "struct usage error";
218 sub _subclass_error {
219 croak 'struct class cannot be a subclass (@ISA not allowed)';
229 Class::Struct - declare struct-like datatypes as Perl classes
234 # declare struct, based on array:
235 struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]);
236 # declare struct, based on hash:
237 struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... });
241 # declare struct, based on array, implicit class name:
242 struct( ELEMENT_NAME => ELEMENT_TYPE, ... );
247 # declare struct with four types of elements:
248 struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' );
250 $obj = new Myobj; # constructor
252 # scalar type accessor:
253 $element_value = $obj->s; # element value
254 $obj->s('new value'); # assign to element
256 # array type accessor:
257 $ary_ref = $obj->a; # reference to whole array
258 $ary_element_value = $obj->a(2); # array element value
259 $obj->a(2, 'new value'); # assign to array element
261 # hash type accessor:
262 $hash_ref = $obj->h; # reference to whole hash
263 $hash_element_value = $obj->h('x'); # hash element value
264 $obj->h('x', 'new value'); # assign to hash element
266 # class type accessor:
267 $element_value = $obj->c; # object reference
268 $obj->c->method(...); # call method of object
269 $obj->c(new My_Other_Class); # assign a new object
274 C<Class::Struct> exports a single function, C<struct>.
275 Given a list of element names and types, and optionally
276 a class name, C<struct> creates a Perl 5 class that implements
277 a "struct-like" data structure.
279 The new class is given a constructor method, C<new>, for creating
282 Each element in the struct data has an accessor method, which is
283 used to assign to the element and to fetch its value. The
284 default accessor can be overridden by declaring a C<sub> of the
285 same name in the package. (See Example 2.)
287 Each element's type can be scalar, array, hash, or class.
290 =head2 The C<struct()> function
292 The C<struct> function has three forms of parameter-list.
294 struct( CLASS_NAME => [ ELEMENT_LIST ]);
295 struct( CLASS_NAME => { ELEMENT_LIST });
296 struct( ELEMENT_LIST );
298 The first and second forms explicitly identify the name of the
299 class being created. The third form assumes the current package
300 name as the class name.
302 An object of a class created by the first and third forms is
303 based on an array, whereas an object of a class created by the
304 second form is based on a hash. The array-based forms will be
305 somewhat faster and smaller; the hash-based forms are more
308 The class created by C<struct> must not be a subclass of another
309 class other than C<UNIVERSAL>.
311 It can, however, be used as a superclass for other classes. To facilitate
312 this, the generated constructor method uses a two-argument blessing.
313 Furthermore, if the class is hash-based, the key of each element is
314 prefixed with the class name (see I<Perl Cookbook>, Recipe 13.12).
316 A function named C<new> must not be explicitly defined in a class
317 created by C<struct>.
319 The I<ELEMENT_LIST> has the form
323 Each name-type pair declares one element of the struct. Each
324 element name will be defined as an accessor method unless a
325 method by that name is explicitly defined; in the latter case, a
326 warning is issued if the warning flag (B<-w>) is set.
329 =head2 Element Types and Accessor Methods
331 The four element types -- scalar, array, hash, and class -- are
332 represented by strings -- C<'$'>, C<'@'>, C<'%'>, and a class name --
333 optionally preceded by a C<'*'>.
335 The accessor method provided by C<struct> for an element depends
336 on the declared type of the element.
340 =item Scalar (C<'$'> or C<'*$'>)
342 The element is a scalar, and by default is initialized to C<undef>
343 (but see L<Initializing with new>).
345 The accessor's argument, if any, is assigned to the element.
347 If the element type is C<'$'>, the value of the element (after
348 assignment) is returned. If the element type is C<'*$'>, a reference
349 to the element is returned.
351 =item Array (C<'@'> or C<'*@'>)
353 The element is an array, initialized by default to C<()>.
355 With no argument, the accessor returns a reference to the
356 element's whole array (whether or not the element was
357 specified as C<'@'> or C<'*@').
359 With one or two arguments, the first argument is an index
360 specifying one element of the array; the second argument, if
361 present, is assigned to the array element. If the element type
362 is C<'@'>, the accessor returns the array element value. If the
363 element type is C<'*@'>, a reference to the array element is
366 =item Hash (C<'%'> or C<'*%'>)
368 The element is a hash, initialized by default to C<()>.
370 With no argument, the accessor returns a reference to the
371 element's whole hash (whether or not the element was
372 specified as C<'%'> or C<'*%').
374 With one or two arguments, the first argument is a key specifying
375 one element of the hash; the second argument, if present, is
376 assigned to the hash element. If the element type is C<'%'>, the
377 accessor returns the hash element value. If the element type is
378 C<'*%'>, a reference to the hash element is returned.
380 =item Class (C<'Class_Name'> or C<'*Class_Name'>)
382 The element's value must be a reference blessed to the named
383 class or to one of its subclasses. The element is initialized to
384 the result of calling the C<new> constructor of the named class.
386 The accessor's argument, if any, is assigned to the element. The
387 accessor will C<croak> if this is not an appropriate object
390 If the element type does not start with a C<'*'>, the accessor
391 returns the element value (after assignment). If the element type
392 starts with a C<'*'>, a reference to the element itself is returned.
396 =head2 Initializing with C<new>
398 C<struct> always creates a constructor called C<new>. That constructor
399 may take a list of initializers for the various elements of the new
402 Each initializer is a pair of values: I<element name>C< =E<gt> >I<value>.
403 The initializer value for a scalar element is just a scalar value. The
404 initializer for an array element is an array reference. The initializer
405 for a hash is a hash reference.
407 The initializer for a class element is also a hash reference, and the
408 contents of that hash are passed to the element's own constructor.
410 See Example 3 below for an example of initialization.
419 Giving a struct element a class type that is also a struct is how
420 structs are nested. Here, C<timeval> represents a time (seconds and
421 microseconds), and C<rusage> has two elements, each of which is of
427 ru_utime => timeval, # seconds
428 ru_stime => timeval, # microseconds
439 # $t->ru_utime and $t->ru_stime are objects of type timeval.
440 # set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec.
441 $t->ru_utime->tv_secs(100);
442 $t->ru_utime->tv_usecs(0);
443 $t->ru_stime->tv_secs(5);
444 $t->ru_stime->tv_usecs(0);
449 An accessor function can be redefined in order to provide
450 additional checking of values, etc. Here, we want the C<count>
451 element always to be nonnegative, so we redefine the C<count>
452 accessor accordingly.
458 struct ( 'MyObj', { count => '$', stuff => '%' } );
460 # override the default accessor method for 'count'
464 die 'count must be nonnegative' if $_[0] < 0;
465 $self->{'count'} = shift;
466 warn "Too many args to count" if @_;
468 return $self->{'count'};
473 print "\$x->count(5) = ", $x->count(5), "\n";
474 # prints '$x->count(5) = 5'
476 print "\$x->count = ", $x->count, "\n";
477 # prints '$x->count = 5'
479 print "\$x->count(-5) = ", $x->count(-5), "\n";
480 # dies due to negative argument!
484 The constructor of a generated class can be passed a list
485 of I<element>=>I<value> pairs, with which to initialize the struct.
486 If no initializer is specified for a particular element, its default
487 initialization is performed instead. Initializers for non-existent
488 elements are silently ignored.
490 Note that the initializer for a nested struct is specified
491 as an anonymous hash of initializers, which is passed on to the nested
492 struct's constructor.
512 my $cat = Cat->new( name => 'Socks',
513 kittens => ['Monica', 'Kenneth'],
514 markings => { socks=>1, blaze=>"white" },
515 breed => { name=>'short-hair', cross=>1 },
518 print "Once a cat called ", $cat->name, "\n";
519 print "(which was a ", $cat->breed->name, ")\n";
520 print "had two kittens: ", join(' and ', @{$cat->kittens}), "\n";
523 =head1 Author and Modification History
526 Modified by Damian Conway, 1999-03-05, v0.58.
528 Added handling of hash-like arg list to class ctor.
530 Changed to two-argument blessing in ctor to support
531 derivation from created classes.
533 Added classname prefixes to keys in hash-based classes
534 (refer to "Perl Cookbook", Recipe 13.12 for rationale).
536 Corrected behaviour of accessors for '*@' and '*%' struct
537 elements. Package now implements documented behaviour when
538 returning a reference to an entire hash or array element.
539 Previously these were returned as a reference to a reference
543 Renamed to C<Class::Struct> and modified by Jim Miner, 1997-04-02.
545 members() function removed.
546 Documentation corrected and extended.
547 Use of struct() in a subclass prohibited.
548 User definition of accessor allowed.
549 Treatment of '*' in element types corrected.
550 Treatment of classes as element types corrected.
551 Class name to struct() made optional.
552 Diagnostic checks added.
555 Originally C<Class::Template> by Dean Roehrich.
557 # Template.pm --- struct/member template builder
561 # changes/bugs fixed since 28nov94 version:
563 # changes/bugs fixed since 21nov94 version:
565 # changes/bugs fixed since 02sep94 version:
566 # - Moved to Class::Template.
567 # changes/bugs fixed since 20feb94 version:
568 # - Updated to be a more proper module.
569 # - Added "use strict".
570 # - Bug in build_methods, was using @var when @$var needed.
571 # - Now using my() rather than local().
573 # Uses perl5 classes to create nested data types.
574 # This is offered as one implementation of Tom Christiansen's "structs.pl"