3 ## See POD after __END__
8 use warnings::register;
9 our(@ISA, @EXPORT, $VERSION);
21 if (@_) { $print = shift }
26 package Class::Struct::Tie_ISA;
30 return bless [], $class;
34 my ($self, $index, $value) = @_;
35 Class::Struct::_subclass_error();
39 my ($self, $index) = @_;
45 return scalar(@$self);
55 $self->export_to_level( 1, $self, @EXPORT );
57 # This is admittedly a little bit silly:
58 # do we ever export anything else than 'struct'...?
59 $self->export_to_level( 1, $self, @_ );
67 # Determine parameter list structure, one of:
68 # struct( class => [ element-list ])
69 # struct( class => { element-list })
70 # struct( element-list )
71 # Latter form assumes current package name as struct name.
74 my $base_type = ref $_[1];
75 if ( $base_type eq 'HASH' ) {
80 elsif ( $base_type eq 'ARRAY' ) {
87 $class = (caller())[0];
91 _usage_error() if @decls % 2 == 1;
93 # Ensure we are not, and will not be, a subclass.
99 _subclass_error() if @$isa;
100 tie @$isa, 'Class::Struct::Tie_ISA';
102 # Create constructor.
104 croak "function 'new' already defined in package $class"
105 if do { no strict 'refs'; defined &{$class . "::new"} };
115 $out = "{\n package $class;\n use Carp;\n sub new {\n";
116 $out .= " my (\$class, \%init) = \@_;\n";
117 $out .= " \$class = __PACKAGE__ unless \@_;\n";
121 my( $cmt, $name, $type, $elem );
123 if( $base_type eq 'HASH' ){
124 $out .= " my(\$r) = {};\n";
127 elsif( $base_type eq 'ARRAY' ){
128 $out .= " my(\$r) = [];\n";
131 $out .= " bless \$r, \$class;\n\n";
133 while( $idx < @decls ){
134 $name = $decls[$idx];
135 $type = $decls[$idx+1];
136 push( @methods, $name );
137 if( $base_type eq 'HASH' ){
138 $elem = "{'${class}::$name'}";
140 elsif( $base_type eq 'ARRAY' ){
145 if( $type =~ /^\*(.)/ ){
149 my $init = "defined(\$init{'$name'}) ? \$init{'$name'} :";
151 $out .= " croak 'Initializer for $name must be array reference'\n";
152 $out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'ARRAY';\n";
153 $out .= " \$r->$name( $init [] );$cmt\n";
156 elsif( $type eq '%' ){
157 $out .= " croak 'Initializer for $name must be hash reference'\n";
158 $out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'HASH';\n";
159 $out .= " \$r->$name( $init {} );$cmt\n";
162 elsif ( $type eq '$') {
163 $out .= " \$r->$name( $init undef );$cmt\n";
165 elsif( $type =~ /^\w+(?:::\w+)*$/ ){
166 $out .= " if (defined(\$init{'$name'})) {\n";
167 $out .= " if (ref \$init{'$name'} eq 'HASH')\n";
168 $out .= " { \$r->$name( $type->new(\%{\$init{'$name'}}) ) } $cmt\n";
169 $out .= " elsif (UNIVERSAL::isa(\$init{'$name'}, '$type'))\n";
170 $out .= " { \$r->$name( \$init{'$name'} ) } $cmt\n";
171 $out .= " else { croak 'Initializer for $name must be hash or $type reference' }\n";
173 $classes{$name} = $type;
177 croak "'$type' is not a valid struct element type";
182 $out .= "\n \$r;\n}\n";
184 # Create accessor methods.
186 my( $pre, $pst, $sel );
188 foreach $name (@methods){
189 if ( do { no strict 'refs'; defined &{$class . "::$name"} } ) {
190 warnings::warnif("function '$name' already defined, overrides struct accessor method");
193 $pre = $pst = $cmt = $sel = '';
194 if( defined $refs{$name} ){
197 $cmt = " # returns ref";
199 $out .= " sub $name {$cmt\n my \$r = shift;\n";
200 if( $base_type eq 'ARRAY' ){
204 elsif( $base_type eq 'HASH' ){
205 $elem = "{'${class}::$name'}";
207 if( defined $arrays{$name} ){
208 $out .= " my \$i;\n";
209 $out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n";
210 $out .= " if (ref(\$i) eq 'ARRAY' && !\@_) { \$r->$elem = \$i; return \$r }\n";
213 elsif( defined $hashes{$name} ){
214 $out .= " my \$i;\n";
215 $out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n";
216 $out .= " if (ref(\$i) eq 'HASH' && !\@_) { \$r->$elem = \$i; return \$r }\n";
219 elsif( defined $classes{$name} ){
220 $out .= " croak '$name argument is wrong class' if \@_ && ! UNIVERSAL::isa(\$_[0], '$classes{$name}');\n";
222 $out .= " croak 'Too many args to $name' if \@_ > 1;\n";
223 $out .= " \@_ ? ($pre\$r->$elem$sel = shift$pst) : $pre\$r->$elem$sel$pst;\n";
229 print $out if $print;
230 my $result = eval $out;
235 confess "struct usage error";
238 sub _subclass_error {
239 croak 'struct class cannot be a subclass (@ISA not allowed)';
249 Class::Struct - declare struct-like datatypes as Perl classes
254 # declare struct, based on array:
255 struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]);
256 # declare struct, based on hash:
257 struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... });
261 # declare struct, based on array, implicit class name:
262 struct( ELEMENT_NAME => ELEMENT_TYPE, ... );
264 # Declare struct at compile time
265 use Class::Struct CLASS_NAME => [ELEMENT_NAME => ELEMENT_TYPE, ...];
266 use Class::Struct CLASS_NAME => {ELEMENT_NAME => ELEMENT_TYPE, ...};
268 # declare struct at compile time, based on array, implicit
271 use Class::Struct ELEMENT_NAME => ELEMENT_TYPE, ... ;
275 # declare struct with four types of elements:
276 struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' );
278 $obj = new Myobj; # constructor
280 # scalar type accessor:
281 $element_value = $obj->s; # element value
282 $obj->s('new value'); # assign to element
284 # array type accessor:
285 $ary_ref = $obj->a; # reference to whole array
286 $ary_element_value = $obj->a(2); # array element value
287 $obj->a(2, 'new value'); # assign to array element
289 # hash type accessor:
290 $hash_ref = $obj->h; # reference to whole hash
291 $hash_element_value = $obj->h('x'); # hash element value
292 $obj->h('x', 'new value'); # assign to hash element
294 # class type accessor:
295 $element_value = $obj->c; # object reference
296 $obj->c->method(...); # call method of object
297 $obj->c(new My_Other_Class); # assign a new object
301 C<Class::Struct> exports a single function, C<struct>.
302 Given a list of element names and types, and optionally
303 a class name, C<struct> creates a Perl 5 class that implements
304 a "struct-like" data structure.
306 The new class is given a constructor method, C<new>, for creating
309 Each element in the struct data has an accessor method, which is
310 used to assign to the element and to fetch its value. The
311 default accessor can be overridden by declaring a C<sub> of the
312 same name in the package. (See Example 2.)
314 Each element's type can be scalar, array, hash, or class.
316 =head2 The C<struct()> function
318 The C<struct> function has three forms of parameter-list.
320 struct( CLASS_NAME => [ ELEMENT_LIST ]);
321 struct( CLASS_NAME => { ELEMENT_LIST });
322 struct( ELEMENT_LIST );
324 The first and second forms explicitly identify the name of the
325 class being created. The third form assumes the current package
326 name as the class name.
328 An object of a class created by the first and third forms is
329 based on an array, whereas an object of a class created by the
330 second form is based on a hash. The array-based forms will be
331 somewhat faster and smaller; the hash-based forms are more
334 The class created by C<struct> must not be a subclass of another
335 class other than C<UNIVERSAL>.
337 It can, however, be used as a superclass for other classes. To facilitate
338 this, the generated constructor method uses a two-argument blessing.
339 Furthermore, if the class is hash-based, the key of each element is
340 prefixed with the class name (see I<Perl Cookbook>, Recipe 13.12).
342 A function named C<new> must not be explicitly defined in a class
343 created by C<struct>.
345 The I<ELEMENT_LIST> has the form
349 Each name-type pair declares one element of the struct. Each
350 element name will be defined as an accessor method unless a
351 method by that name is explicitly defined; in the latter case, a
352 warning is issued if the warning flag (B<-w>) is set.
354 =head2 Class Creation at Compile Time
356 C<Class::Struct> can create your class at compile time. The main reason
357 for doing this is obvious, so your class acts like every other class in
358 Perl. Creating your class at compile time will make the order of events
359 similar to using any other class ( or Perl module ).
361 There is no significant speed gain between compile time and run time
362 class creation, there is just a new, more standard order of events.
364 =head2 Element Types and Accessor Methods
366 The four element types -- scalar, array, hash, and class -- are
367 represented by strings -- C<'$'>, C<'@'>, C<'%'>, and a class name --
368 optionally preceded by a C<'*'>.
370 The accessor method provided by C<struct> for an element depends
371 on the declared type of the element.
375 =item Scalar (C<'$'> or C<'*$'>)
377 The element is a scalar, and by default is initialized to C<undef>
378 (but see L<Initializing with new>).
380 The accessor's argument, if any, is assigned to the element.
382 If the element type is C<'$'>, the value of the element (after
383 assignment) is returned. If the element type is C<'*$'>, a reference
384 to the element is returned.
386 =item Array (C<'@'> or C<'*@'>)
388 The element is an array, initialized by default to C<()>.
390 With no argument, the accessor returns a reference to the
391 element's whole array (whether or not the element was
392 specified as C<'@'> or C<'*@'>).
394 With one or two arguments, the first argument is an index
395 specifying one element of the array; the second argument, if
396 present, is assigned to the array element. If the element type
397 is C<'@'>, the accessor returns the array element value. If the
398 element type is C<'*@'>, a reference to the array element is
401 As a special case, when the accessor is called with an array reference
402 as the sole argument, this causes an assignment of the whole array element.
403 The object reference is returned.
405 =item Hash (C<'%'> or C<'*%'>)
407 The element is a hash, initialized by default to C<()>.
409 With no argument, the accessor returns a reference to the
410 element's whole hash (whether or not the element was
411 specified as C<'%'> or C<'*%'>).
413 With one or two arguments, the first argument is a key specifying
414 one element of the hash; the second argument, if present, is
415 assigned to the hash element. If the element type is C<'%'>, the
416 accessor returns the hash element value. If the element type is
417 C<'*%'>, a reference to the hash element is returned.
419 As a special case, when the accessor is called with a hash reference
420 as the sole argument, this causes an assignment of the whole hash element.
421 The object reference is returned.
423 =item Class (C<'Class_Name'> or C<'*Class_Name'>)
425 The element's value must be a reference blessed to the named
426 class or to one of its subclasses. The element is not initialized
429 The accessor's argument, if any, is assigned to the element. The
430 accessor will C<croak> if this is not an appropriate object
433 If the element type does not start with a C<'*'>, the accessor
434 returns the element value (after assignment). If the element type
435 starts with a C<'*'>, a reference to the element itself is returned.
439 =head2 Initializing with C<new>
441 C<struct> always creates a constructor called C<new>. That constructor
442 may take a list of initializers for the various elements of the new
445 Each initializer is a pair of values: I<element name>C< =E<gt> >I<value>.
446 The initializer value for a scalar element is just a scalar value. The
447 initializer for an array element is an array reference. The initializer
448 for a hash is a hash reference.
450 The initializer for a class element is an object of the corresponding class,
451 or of one of it's subclasses, or a reference to a hash containing named
452 arguments to be passed to the element's constructor.
454 See Example 3 below for an example of initialization.
462 Giving a struct element a class type that is also a struct is how
463 structs are nested. Here, C<Timeval> represents a time (seconds and
464 microseconds), and C<Rusage> has two elements, each of which is of
470 ru_utime => 'Timeval', # user time used
471 ru_stime => 'Timeval', # system time used
475 tv_secs => '$', # seconds
476 tv_usecs => '$', # microseconds
480 my $t = Rusage->new(ru_utime=>Timeval->new(),
481 ru_stime=>Timeval->new());
483 # $t->ru_utime and $t->ru_stime are objects of type Timeval.
484 # set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec.
485 $t->ru_utime->tv_secs(100);
486 $t->ru_utime->tv_usecs(0);
487 $t->ru_stime->tv_secs(5);
488 $t->ru_stime->tv_usecs(0);
492 An accessor function can be redefined in order to provide
493 additional checking of values, etc. Here, we want the C<count>
494 element always to be nonnegative, so we redefine the C<count>
495 accessor accordingly.
501 struct ( 'MyObj', { count => '$', stuff => '%' } );
503 # override the default accessor method for 'count'
507 die 'count must be nonnegative' if $_[0] < 0;
508 $self->{'MyObj::count'} = shift;
509 warn "Too many args to count" if @_;
511 return $self->{'MyObj::count'};
516 print "\$x->count(5) = ", $x->count(5), "\n";
517 # prints '$x->count(5) = 5'
519 print "\$x->count = ", $x->count, "\n";
520 # prints '$x->count = 5'
522 print "\$x->count(-5) = ", $x->count(-5), "\n";
523 # dies due to negative argument!
527 The constructor of a generated class can be passed a list
528 of I<element>=>I<value> pairs, with which to initialize the struct.
529 If no initializer is specified for a particular element, its default
530 initialization is performed instead. Initializers for non-existent
531 elements are silently ignored.
533 Note that the initializer for a nested class may be specified as
534 an object of that class, or as a reference to a hash of initializers
535 that are passed on to the nested struct's constructor.
554 my $cat = Cat->new( name => 'Socks',
555 kittens => ['Monica', 'Kenneth'],
556 markings => { socks=>1, blaze=>"white" },
557 breed => Breed->new(name=>'short-hair', cross=>1),
558 or: breed => {name=>'short-hair', cross=>1},
561 print "Once a cat called ", $cat->name, "\n";
562 print "(which was a ", $cat->breed->name, ")\n";
563 print "had 2 kittens: ", join(' and ', @{$cat->kittens}), "\n";
567 =head1 Author and Modification History
569 Modified by Damian Conway, 2001-09-10, v0.62.
571 Modified implicit construction of nested objects.
572 Now will also take an object ref instead of requiring a hash ref.
573 Also default initializes nested object attributes to undef, rather
574 than calling object constructor without args
575 Original over-helpfulness was fraught with problems:
576 * the class's constructor might not be called 'new'
577 * the class might not have a hash-like-arguments constructor
578 * the class might not have a no-argument constructor
579 * "recursive" data structures didn't work well:
581 struct { mother => 'Person', father => 'Person'};
584 Modified by Casey West, 2000-11-08, v0.59.
586 Added the ability for compile time class creation.
588 Modified by Damian Conway, 1999-03-05, v0.58.
590 Added handling of hash-like arg list to class ctor.
592 Changed to two-argument blessing in ctor to support
593 derivation from created classes.
595 Added classname prefixes to keys in hash-based classes
596 (refer to "Perl Cookbook", Recipe 13.12 for rationale).
598 Corrected behaviour of accessors for '*@' and '*%' struct
599 elements. Package now implements documented behaviour when
600 returning a reference to an entire hash or array element.
601 Previously these were returned as a reference to a reference
604 Renamed to C<Class::Struct> and modified by Jim Miner, 1997-04-02.
606 members() function removed.
607 Documentation corrected and extended.
608 Use of struct() in a subclass prohibited.
609 User definition of accessor allowed.
610 Treatment of '*' in element types corrected.
611 Treatment of classes as element types corrected.
612 Class name to struct() made optional.
613 Diagnostic checks added.
615 Originally C<Class::Template> by Dean Roehrich.
617 # Template.pm --- struct/member template builder
621 # changes/bugs fixed since 28nov94 version:
623 # changes/bugs fixed since 21nov94 version:
625 # changes/bugs fixed since 02sep94 version:
626 # - Moved to Class::Template.
627 # changes/bugs fixed since 20feb94 version:
628 # - Updated to be a more proper module.
629 # - Added "use strict".
630 # - Bug in build_methods, was using @var when @$var needed.
631 # - Now using my() rather than local().
633 # Uses perl5 classes to create nested data types.
634 # This is offered as one implementation of Tom Christiansen's