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 . "::$name"} } ) {
171 warnings::warnif("function '$name' already defined, overrides struct accessor method");
174 $pre = $pst = $cmt = $sel = '';
175 if( defined $refs{$name} ){
178 $cmt = " # returns ref";
180 $out .= " sub $name {$cmt\n my \$r = shift;\n";
181 if( $base_type eq 'ARRAY' ){
185 elsif( $base_type eq 'HASH' ){
186 $elem = "{'${class}::$name'}";
188 if( defined $arrays{$name} ){
189 $out .= " my \$i;\n";
190 $out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n";
193 elsif( defined $hashes{$name} ){
194 $out .= " my \$i;\n";
195 $out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n";
198 elsif( defined $classes{$name} ){
199 if ( $CHECK_CLASS_MEMBERSHIP ) {
200 $out .= " croak '$name argument is wrong class' if \@_ && ! UNIVERSAL::isa(\$_[0], '$classes{$name}');\n";
203 $out .= " croak 'Too many args to $name' if \@_ > 1;\n";
204 $out .= " \@_ ? ($pre\$r->$elem$sel = shift$pst) : $pre\$r->$elem$sel$pst;\n";
210 print $out if $print;
211 my $result = eval $out;
216 confess "struct usage error";
219 sub _subclass_error {
220 croak 'struct class cannot be a subclass (@ISA not allowed)';
230 Class::Struct - declare struct-like datatypes as Perl classes
235 # declare struct, based on array:
236 struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]);
237 # declare struct, based on hash:
238 struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... });
242 # declare struct, based on array, implicit class name:
243 struct( ELEMENT_NAME => ELEMENT_TYPE, ... );
248 # declare struct with four types of elements:
249 struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' );
251 $obj = new Myobj; # constructor
253 # scalar type accessor:
254 $element_value = $obj->s; # element value
255 $obj->s('new value'); # assign to element
257 # array type accessor:
258 $ary_ref = $obj->a; # reference to whole array
259 $ary_element_value = $obj->a(2); # array element value
260 $obj->a(2, 'new value'); # assign to array element
262 # hash type accessor:
263 $hash_ref = $obj->h; # reference to whole hash
264 $hash_element_value = $obj->h('x'); # hash element value
265 $obj->h('x', 'new value'); # assign to hash element
267 # class type accessor:
268 $element_value = $obj->c; # object reference
269 $obj->c->method(...); # call method of object
270 $obj->c(new My_Other_Class); # assign a new object
275 C<Class::Struct> exports a single function, C<struct>.
276 Given a list of element names and types, and optionally
277 a class name, C<struct> creates a Perl 5 class that implements
278 a "struct-like" data structure.
280 The new class is given a constructor method, C<new>, for creating
283 Each element in the struct data has an accessor method, which is
284 used to assign to the element and to fetch its value. The
285 default accessor can be overridden by declaring a C<sub> of the
286 same name in the package. (See Example 2.)
288 Each element's type can be scalar, array, hash, or class.
291 =head2 The C<struct()> function
293 The C<struct> function has three forms of parameter-list.
295 struct( CLASS_NAME => [ ELEMENT_LIST ]);
296 struct( CLASS_NAME => { ELEMENT_LIST });
297 struct( ELEMENT_LIST );
299 The first and second forms explicitly identify the name of the
300 class being created. The third form assumes the current package
301 name as the class name.
303 An object of a class created by the first and third forms is
304 based on an array, whereas an object of a class created by the
305 second form is based on a hash. The array-based forms will be
306 somewhat faster and smaller; the hash-based forms are more
309 The class created by C<struct> must not be a subclass of another
310 class other than C<UNIVERSAL>.
312 It can, however, be used as a superclass for other classes. To facilitate
313 this, the generated constructor method uses a two-argument blessing.
314 Furthermore, if the class is hash-based, the key of each element is
315 prefixed with the class name (see I<Perl Cookbook>, Recipe 13.12).
317 A function named C<new> must not be explicitly defined in a class
318 created by C<struct>.
320 The I<ELEMENT_LIST> has the form
324 Each name-type pair declares one element of the struct. Each
325 element name will be defined as an accessor method unless a
326 method by that name is explicitly defined; in the latter case, a
327 warning is issued if the warning flag (B<-w>) is set.
330 =head2 Element Types and Accessor Methods
332 The four element types -- scalar, array, hash, and class -- are
333 represented by strings -- C<'$'>, C<'@'>, C<'%'>, and a class name --
334 optionally preceded by a C<'*'>.
336 The accessor method provided by C<struct> for an element depends
337 on the declared type of the element.
341 =item Scalar (C<'$'> or C<'*$'>)
343 The element is a scalar, and by default is initialized to C<undef>
344 (but see L<Initializing with new>).
346 The accessor's argument, if any, is assigned to the element.
348 If the element type is C<'$'>, the value of the element (after
349 assignment) is returned. If the element type is C<'*$'>, a reference
350 to the element is returned.
352 =item Array (C<'@'> or C<'*@'>)
354 The element is an array, initialized by default to C<()>.
356 With no argument, the accessor returns a reference to the
357 element's whole array (whether or not the element was
358 specified as C<'@'> or C<'*@'>).
360 With one or two arguments, the first argument is an index
361 specifying one element of the array; the second argument, if
362 present, is assigned to the array element. If the element type
363 is C<'@'>, the accessor returns the array element value. If the
364 element type is C<'*@'>, a reference to the array element is
367 =item Hash (C<'%'> or C<'*%'>)
369 The element is a hash, initialized by default to C<()>.
371 With no argument, the accessor returns a reference to the
372 element's whole hash (whether or not the element was
373 specified as C<'%'> or C<'*%'>).
375 With one or two arguments, the first argument is a key specifying
376 one element of the hash; the second argument, if present, is
377 assigned to the hash element. If the element type is C<'%'>, the
378 accessor returns the hash element value. If the element type is
379 C<'*%'>, a reference to the hash element is returned.
381 =item Class (C<'Class_Name'> or C<'*Class_Name'>)
383 The element's value must be a reference blessed to the named
384 class or to one of its subclasses. The element is initialized to
385 the result of calling the C<new> constructor of the named class.
387 The accessor's argument, if any, is assigned to the element. The
388 accessor will C<croak> if this is not an appropriate object
391 If the element type does not start with a C<'*'>, the accessor
392 returns the element value (after assignment). If the element type
393 starts with a C<'*'>, a reference to the element itself is returned.
397 =head2 Initializing with C<new>
399 C<struct> always creates a constructor called C<new>. That constructor
400 may take a list of initializers for the various elements of the new
403 Each initializer is a pair of values: I<element name>C< =E<gt> >I<value>.
404 The initializer value for a scalar element is just a scalar value. The
405 initializer for an array element is an array reference. The initializer
406 for a hash is a hash reference.
408 The initializer for a class element is also a hash reference, and the
409 contents of that hash are passed to the element's own constructor.
411 See Example 3 below for an example of initialization.
420 Giving a struct element a class type that is also a struct is how
421 structs are nested. Here, C<timeval> represents a time (seconds and
422 microseconds), and C<rusage> has two elements, each of which is of
428 ru_utime => timeval, # seconds
429 ru_stime => timeval, # microseconds
440 # $t->ru_utime and $t->ru_stime are objects of type timeval.
441 # set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec.
442 $t->ru_utime->tv_secs(100);
443 $t->ru_utime->tv_usecs(0);
444 $t->ru_stime->tv_secs(5);
445 $t->ru_stime->tv_usecs(0);
450 An accessor function can be redefined in order to provide
451 additional checking of values, etc. Here, we want the C<count>
452 element always to be nonnegative, so we redefine the C<count>
453 accessor accordingly.
459 struct ( 'MyObj', { count => '$', stuff => '%' } );
461 # override the default accessor method for 'count'
465 die 'count must be nonnegative' if $_[0] < 0;
466 $self->{'count'} = shift;
467 warn "Too many args to count" if @_;
469 return $self->{'count'};
474 print "\$x->count(5) = ", $x->count(5), "\n";
475 # prints '$x->count(5) = 5'
477 print "\$x->count = ", $x->count, "\n";
478 # prints '$x->count = 5'
480 print "\$x->count(-5) = ", $x->count(-5), "\n";
481 # dies due to negative argument!
485 The constructor of a generated class can be passed a list
486 of I<element>=>I<value> pairs, with which to initialize the struct.
487 If no initializer is specified for a particular element, its default
488 initialization is performed instead. Initializers for non-existent
489 elements are silently ignored.
491 Note that the initializer for a nested struct is specified
492 as an anonymous hash of initializers, which is passed on to the nested
493 struct's constructor.
513 my $cat = Cat->new( name => 'Socks',
514 kittens => ['Monica', 'Kenneth'],
515 markings => { socks=>1, blaze=>"white" },
516 breed => { name=>'short-hair', cross=>1 },
519 print "Once a cat called ", $cat->name, "\n";
520 print "(which was a ", $cat->breed->name, ")\n";
521 print "had two kittens: ", join(' and ', @{$cat->kittens}), "\n";
525 =head1 Author and Modification History
528 Modified by Damian Conway, 1999-03-05, v0.58.
530 Added handling of hash-like arg list to class ctor.
532 Changed to two-argument blessing in ctor to support
533 derivation from created classes.
535 Added classname prefixes to keys in hash-based classes
536 (refer to "Perl Cookbook", Recipe 13.12 for rationale).
538 Corrected behaviour of accessors for '*@' and '*%' struct
539 elements. Package now implements documented behaviour when
540 returning a reference to an entire hash or array element.
541 Previously these were returned as a reference to a reference
545 Renamed to C<Class::Struct> and modified by Jim Miner, 1997-04-02.
547 members() function removed.
548 Documentation corrected and extended.
549 Use of struct() in a subclass prohibited.
550 User definition of accessor allowed.
551 Treatment of '*' in element types corrected.
552 Treatment of classes as element types corrected.
553 Class name to struct() made optional.
554 Diagnostic checks added.
557 Originally C<Class::Template> by Dean Roehrich.
559 # Template.pm --- struct/member template builder
563 # changes/bugs fixed since 28nov94 version:
565 # changes/bugs fixed since 21nov94 version:
567 # changes/bugs fixed since 02sep94 version:
568 # - Moved to Class::Template.
569 # changes/bugs fixed since 20feb94 version:
570 # - Updated to be a more proper module.
571 # - Added "use strict".
572 # - Bug in build_methods, was using @var when @$var needed.
573 # - Now using my() rather than local().
575 # Uses perl5 classes to create nested data types.
576 # This is offered as one implementation of Tom Christiansen's "structs.pl"