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1 | package Class::Struct; |
2 | |
3 | ## See POD after __END__ |
4 | |
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5 | use 5.005_64; |
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6 | |
7 | use strict; |
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8 | use warnings::register; |
17f410f9 |
9 | our(@ISA, @EXPORT, $VERSION); |
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10 | |
11 | use Carp; |
12 | |
13 | require Exporter; |
14 | @ISA = qw(Exporter); |
15 | @EXPORT = qw(struct); |
16 | |
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17 | $VERSION = '0.58'; |
18 | |
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19 | ## Tested on 5.002 and 5.003 without class membership tests: |
20 | my $CHECK_CLASS_MEMBERSHIP = ($] >= 5.003_95); |
21 | |
22 | my $print = 0; |
23 | sub printem { |
24 | if (@_) { $print = shift } |
25 | else { $print++ } |
26 | } |
27 | |
28 | { |
29 | package Class::Struct::Tie_ISA; |
30 | |
31 | sub TIEARRAY { |
32 | my $class = shift; |
33 | return bless [], $class; |
34 | } |
35 | |
36 | sub STORE { |
37 | my ($self, $index, $value) = @_; |
38 | Class::Struct::_subclass_error(); |
39 | } |
40 | |
41 | sub FETCH { |
42 | my ($self, $index) = @_; |
43 | $self->[$index]; |
44 | } |
45 | |
f740b751 |
46 | sub FETCHSIZE { |
47 | my $self = shift; |
48 | return scalar(@$self); |
49 | } |
50 | |
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51 | sub DESTROY { } |
52 | } |
53 | |
54 | sub struct { |
55 | |
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. |
61 | |
62 | my ($class, @decls); |
63 | my $base_type = ref $_[1]; |
64 | if ( $base_type eq 'HASH' ) { |
65 | $class = shift; |
66 | @decls = %{shift()}; |
67 | _usage_error() if @_; |
68 | } |
69 | elsif ( $base_type eq 'ARRAY' ) { |
70 | $class = shift; |
71 | @decls = @{shift()}; |
72 | _usage_error() if @_; |
73 | } |
74 | else { |
75 | $base_type = 'ARRAY'; |
76 | $class = (caller())[0]; |
77 | @decls = @_; |
78 | } |
79 | _usage_error() if @decls % 2 == 1; |
80 | |
81 | # Ensure we are not, and will not be, a subclass. |
82 | |
83 | my $isa = do { |
84 | no strict 'refs'; |
85 | \@{$class . '::ISA'}; |
86 | }; |
87 | _subclass_error() if @$isa; |
88 | tie @$isa, 'Class::Struct::Tie_ISA'; |
89 | |
90 | # Create constructor. |
91 | |
92 | croak "function 'new' already defined in package $class" |
93 | if do { no strict 'refs'; defined &{$class . "::new"} }; |
94 | |
95 | my @methods = (); |
96 | my %refs = (); |
97 | my %arrays = (); |
98 | my %hashes = (); |
99 | my %classes = (); |
100 | my $got_class = 0; |
101 | my $out = ''; |
102 | |
103 | $out = "{\n package $class;\n use Carp;\n sub new {\n"; |
430530ea |
104 | $out .= " my (\$class, \%init) = \@_;\n"; |
f01e5ef6 |
105 | $out .= " \$class = __PACKAGE__ unless \@_;\n"; |
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106 | |
107 | my $cnt = 0; |
108 | my $idx = 0; |
109 | my( $cmt, $name, $type, $elem ); |
110 | |
111 | if( $base_type eq 'HASH' ){ |
112 | $out .= " my(\$r) = {};\n"; |
113 | $cmt = ''; |
114 | } |
115 | elsif( $base_type eq 'ARRAY' ){ |
116 | $out .= " my(\$r) = [];\n"; |
117 | } |
118 | while( $idx < @decls ){ |
119 | $name = $decls[$idx]; |
120 | $type = $decls[$idx+1]; |
121 | push( @methods, $name ); |
122 | if( $base_type eq 'HASH' ){ |
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123 | $elem = "{'${class}::$name'}"; |
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124 | } |
125 | elsif( $base_type eq 'ARRAY' ){ |
126 | $elem = "[$cnt]"; |
127 | ++$cnt; |
128 | $cmt = " # $name"; |
129 | } |
130 | if( $type =~ /^\*(.)/ ){ |
131 | $refs{$name}++; |
132 | $type = $1; |
133 | } |
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134 | my $init = "defined(\$init{'$name'}) ? \$init{'$name'} :"; |
8cc95fdb |
135 | if( $type eq '@' ){ |
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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"; |
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139 | $arrays{$name}++; |
140 | } |
141 | elsif( $type eq '%' ){ |
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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"; |
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145 | $hashes{$name}++; |
146 | } |
147 | elsif ( $type eq '$') { |
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148 | $out .= " \$r->$elem = $init undef;$cmt\n"; |
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149 | } |
150 | elsif( $type =~ /^\w+(?:::\w+)*$/ ){ |
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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"; |
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155 | $classes{$name} = $type; |
156 | $got_class = 1; |
157 | } |
158 | else{ |
159 | croak "'$type' is not a valid struct element type"; |
160 | } |
161 | $idx += 2; |
162 | } |
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163 | $out .= " bless \$r, \$class;\n }\n"; |
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164 | |
165 | # Create accessor methods. |
166 | |
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167 | my( $pre, $pst, $sel ); |
168 | $cnt = 0; |
169 | foreach $name (@methods){ |
170 | if ( do { no strict 'refs'; defined &{$class . "::$name"} } ) { |
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171 | warnings::warn "function '$name' already defined, overrides struct accessor method" |
172 | if warnings::enabled(); |
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173 | } |
174 | else { |
175 | $pre = $pst = $cmt = $sel = ''; |
176 | if( defined $refs{$name} ){ |
177 | $pre = "\\("; |
178 | $pst = ")"; |
179 | $cmt = " # returns ref"; |
180 | } |
181 | $out .= " sub $name {$cmt\n my \$r = shift;\n"; |
182 | if( $base_type eq 'ARRAY' ){ |
183 | $elem = "[$cnt]"; |
184 | ++$cnt; |
185 | } |
186 | elsif( $base_type eq 'HASH' ){ |
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187 | $elem = "{'${class}::$name'}"; |
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188 | } |
189 | if( defined $arrays{$name} ){ |
190 | $out .= " my \$i;\n"; |
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191 | $out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n"; |
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192 | $sel = "->[\$i]"; |
193 | } |
194 | elsif( defined $hashes{$name} ){ |
195 | $out .= " my \$i;\n"; |
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196 | $out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n"; |
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197 | $sel = "->{\$i}"; |
198 | } |
199 | elsif( defined $classes{$name} ){ |
200 | if ( $CHECK_CLASS_MEMBERSHIP ) { |
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201 | $out .= " croak '$name argument is wrong class' if \@_ && ! UNIVERSAL::isa(\$_[0], '$classes{$name}');\n"; |
8cc95fdb |
202 | } |
203 | } |
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"; |
206 | $out .= " }\n"; |
207 | } |
208 | } |
209 | $out .= "}\n1;\n"; |
210 | |
211 | print $out if $print; |
212 | my $result = eval $out; |
213 | carp $@ if $@; |
214 | } |
215 | |
216 | sub _usage_error { |
217 | confess "struct usage error"; |
218 | } |
219 | |
220 | sub _subclass_error { |
221 | croak 'struct class cannot be a subclass (@ISA not allowed)'; |
222 | } |
223 | |
224 | 1; # for require |
225 | |
226 | |
227 | __END__ |
228 | |
229 | =head1 NAME |
230 | |
231 | Class::Struct - declare struct-like datatypes as Perl classes |
232 | |
233 | =head1 SYNOPSIS |
234 | |
235 | use Class::Struct; |
236 | # declare struct, based on array: |
237 | struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]); |
238 | # declare struct, based on hash: |
239 | struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... }); |
240 | |
241 | package CLASS_NAME; |
242 | use Class::Struct; |
243 | # declare struct, based on array, implicit class name: |
244 | struct( ELEMENT_NAME => ELEMENT_TYPE, ... ); |
245 | |
246 | |
247 | package Myobj; |
248 | use Class::Struct; |
249 | # declare struct with four types of elements: |
250 | struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' ); |
251 | |
252 | $obj = new Myobj; # constructor |
253 | |
254 | # scalar type accessor: |
255 | $element_value = $obj->s; # element value |
256 | $obj->s('new value'); # assign to element |
257 | |
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 |
262 | |
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 |
267 | |
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 |
272 | |
273 | |
274 | =head1 DESCRIPTION |
275 | |
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. |
280 | |
281 | The new class is given a constructor method, C<new>, for creating |
282 | struct objects. |
283 | |
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.) |
288 | |
289 | Each element's type can be scalar, array, hash, or class. |
290 | |
291 | |
292 | =head2 The C<struct()> function |
293 | |
294 | The C<struct> function has three forms of parameter-list. |
295 | |
296 | struct( CLASS_NAME => [ ELEMENT_LIST ]); |
297 | struct( CLASS_NAME => { ELEMENT_LIST }); |
298 | struct( ELEMENT_LIST ); |
299 | |
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. |
303 | |
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 |
308 | flexible. |
309 | |
310 | The class created by C<struct> must not be a subclass of another |
311 | class other than C<UNIVERSAL>. |
312 | |
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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). |
317 | |
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318 | A function named C<new> must not be explicitly defined in a class |
319 | created by C<struct>. |
320 | |
321 | The I<ELEMENT_LIST> has the form |
322 | |
323 | NAME => TYPE, ... |
324 | |
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 |
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328 | warning is issued if the warning flag (B<-w>) is set. |
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329 | |
330 | |
331 | =head2 Element Types and Accessor Methods |
332 | |
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<'*'>. |
336 | |
337 | The accessor method provided by C<struct> for an element depends |
338 | on the declared type of the element. |
339 | |
340 | =over |
341 | |
342 | =item Scalar (C<'$'> or C<'*$'>) |
343 | |
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344 | The element is a scalar, and by default is initialized to C<undef> |
345 | (but see L<Initializing with new>). |
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346 | |
347 | The accessor's argument, if any, is assigned to the element. |
348 | |
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. |
352 | |
353 | =item Array (C<'@'> or C<'*@'>) |
354 | |
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355 | The element is an array, initialized by default to C<()>. |
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356 | |
357 | With no argument, the accessor returns a reference to the |
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358 | element's whole array (whether or not the element was |
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359 | specified as C<'@'> or C<'*@'>). |
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360 | |
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 |
366 | returned. |
367 | |
368 | =item Hash (C<'%'> or C<'*%'>) |
369 | |
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370 | The element is a hash, initialized by default to C<()>. |
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371 | |
372 | With no argument, the accessor returns a reference to the |
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373 | element's whole hash (whether or not the element was |
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374 | specified as C<'%'> or C<'*%'>). |
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375 | |
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. |
381 | |
382 | =item Class (C<'Class_Name'> or C<'*Class_Name'>) |
383 | |
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. |
387 | |
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 |
390 | reference. |
391 | |
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. |
395 | |
396 | =back |
397 | |
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398 | =head2 Initializing with C<new> |
399 | |
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 |
402 | struct. |
403 | |
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. |
408 | |
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. |
411 | |
412 | See Example 3 below for an example of initialization. |
413 | |
414 | |
8cc95fdb |
415 | =head1 EXAMPLES |
416 | |
417 | =over |
418 | |
419 | =item Example 1 |
420 | |
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 |
424 | type C<timeval>. |
425 | |
426 | use Class::Struct; |
427 | |
428 | struct( rusage => { |
429 | ru_utime => timeval, # seconds |
430 | ru_stime => timeval, # microseconds |
431 | }); |
432 | |
433 | struct( timeval => [ |
434 | tv_secs => '$', |
435 | tv_usecs => '$', |
436 | ]); |
437 | |
438 | # create an object: |
439 | my $t = new rusage; |
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440 | |
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441 | # $t->ru_utime and $t->ru_stime are objects of type timeval. |
8cc95fdb |
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 | $t->ru_stime->tv_usecs(0); |
447 | |
448 | |
449 | =item Example 2 |
450 | |
451 | An accessor function can be redefined in order to provide |
452 | additional checking of values, etc. Here, we want the C<count> |
453 | element always to be nonnegative, so we redefine the C<count> |
454 | accessor accordingly. |
455 | |
456 | package MyObj; |
457 | use Class::Struct; |
458 | |
430530ea |
459 | # declare the struct |
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460 | struct ( 'MyObj', { count => '$', stuff => '%' } ); |
461 | |
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462 | # override the default accessor method for 'count' |
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463 | sub count { |
464 | my $self = shift; |
465 | if ( @_ ) { |
466 | die 'count must be nonnegative' if $_[0] < 0; |
467 | $self->{'count'} = shift; |
468 | warn "Too many args to count" if @_; |
469 | } |
470 | return $self->{'count'}; |
471 | } |
472 | |
473 | package main; |
474 | $x = new MyObj; |
475 | print "\$x->count(5) = ", $x->count(5), "\n"; |
476 | # prints '$x->count(5) = 5' |
477 | |
478 | print "\$x->count = ", $x->count, "\n"; |
479 | # prints '$x->count = 5' |
480 | |
481 | print "\$x->count(-5) = ", $x->count(-5), "\n"; |
482 | # dies due to negative argument! |
483 | |
430530ea |
484 | =item Example 3 |
485 | |
486 | The constructor of a generated class can be passed a list |
487 | of I<element>=>I<value> pairs, with which to initialize the struct. |
488 | If no initializer is specified for a particular element, its default |
489 | initialization is performed instead. Initializers for non-existent |
490 | elements are silently ignored. |
491 | |
492 | Note that the initializer for a nested struct is specified |
493 | as an anonymous hash of initializers, which is passed on to the nested |
494 | struct's constructor. |
495 | |
496 | |
497 | use Class::Struct; |
498 | |
499 | struct Breed => |
500 | { |
501 | name => '$', |
502 | cross => '$', |
503 | }; |
504 | |
505 | struct Cat => |
506 | [ |
507 | name => '$', |
508 | kittens => '@', |
509 | markings => '%', |
510 | breed => 'Breed', |
511 | ]; |
512 | |
513 | |
514 | my $cat = Cat->new( name => 'Socks', |
515 | kittens => ['Monica', 'Kenneth'], |
516 | markings => { socks=>1, blaze=>"white" }, |
517 | breed => { name=>'short-hair', cross=>1 }, |
518 | ); |
519 | |
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"; |
523 | |
a45bd81d |
524 | =back |
8cc95fdb |
525 | |
526 | =head1 Author and Modification History |
527 | |
528 | |
430530ea |
529 | Modified by Damian Conway, 1999-03-05, v0.58. |
530 | |
531 | Added handling of hash-like arg list to class ctor. |
532 | |
533 | Changed to two-argument blessing in ctor to support |
534 | derivation from created classes. |
535 | |
536 | Added classname prefixes to keys in hash-based classes |
537 | (refer to "Perl Cookbook", Recipe 13.12 for rationale). |
538 | |
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 |
543 | to the element. |
544 | |
545 | |
8cc95fdb |
546 | Renamed to C<Class::Struct> and modified by Jim Miner, 1997-04-02. |
547 | |
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. |
556 | |
557 | |
558 | Originally C<Class::Template> by Dean Roehrich. |
559 | |
560 | # Template.pm --- struct/member template builder |
561 | # 12mar95 |
562 | # Dean Roehrich |
563 | # |
564 | # changes/bugs fixed since 28nov94 version: |
565 | # - podified |
566 | # changes/bugs fixed since 21nov94 version: |
567 | # - Fixed examples. |
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(). |
575 | # |
576 | # Uses perl5 classes to create nested data types. |
577 | # This is offered as one implementation of Tom Christiansen's "structs.pl" |
578 | # idea. |
579 | |
580 | =cut |