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| 128 | .rm #[ #] #H #V #F C |
| 129 | .\" ======================================================================== |
| 130 | .\" |
| 131 | .IX Title "Class::Struct 3" |
| 132 | .TH Class::Struct 3 "2001-09-21" "perl v5.8.8" "Perl Programmers Reference Guide" |
| 133 | .SH "NAME" |
| 134 | Class::Struct \- declare struct\-like datatypes as Perl classes |
| 135 | .SH "SYNOPSIS" |
| 136 | .IX Header "SYNOPSIS" |
| 137 | .Vb 5 |
| 138 | \& use Class::Struct; |
| 139 | \& # declare struct, based on array: |
| 140 | \& struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]); |
| 141 | \& # declare struct, based on hash: |
| 142 | \& struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... }); |
| 143 | .Ve |
| 144 | .PP |
| 145 | .Vb 4 |
| 146 | \& package CLASS_NAME; |
| 147 | \& use Class::Struct; |
| 148 | \& # declare struct, based on array, implicit class name: |
| 149 | \& struct( ELEMENT_NAME => ELEMENT_TYPE, ... ); |
| 150 | .Ve |
| 151 | .PP |
| 152 | .Vb 3 |
| 153 | \& # Declare struct at compile time |
| 154 | \& use Class::Struct CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]; |
| 155 | \& use Class::Struct CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... }; |
| 156 | .Ve |
| 157 | .PP |
| 158 | .Vb 3 |
| 159 | \& # declare struct at compile time, based on array, implicit class name: |
| 160 | \& package CLASS_NAME; |
| 161 | \& use Class::Struct ELEMENT_NAME => ELEMENT_TYPE, ... ; |
| 162 | .Ve |
| 163 | .PP |
| 164 | .Vb 4 |
| 165 | \& package Myobj; |
| 166 | \& use Class::Struct; |
| 167 | \& # declare struct with four types of elements: |
| 168 | \& struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' ); |
| 169 | .Ve |
| 170 | .PP |
| 171 | .Vb 1 |
| 172 | \& $obj = new Myobj; # constructor |
| 173 | .Ve |
| 174 | .PP |
| 175 | .Vb 3 |
| 176 | \& # scalar type accessor: |
| 177 | \& $element_value = $obj->s; # element value |
| 178 | \& $obj->s('new value'); # assign to element |
| 179 | .Ve |
| 180 | .PP |
| 181 | .Vb 4 |
| 182 | \& # array type accessor: |
| 183 | \& $ary_ref = $obj->a; # reference to whole array |
| 184 | \& $ary_element_value = $obj->a(2); # array element value |
| 185 | \& $obj->a(2, 'new value'); # assign to array element |
| 186 | .Ve |
| 187 | .PP |
| 188 | .Vb 4 |
| 189 | \& # hash type accessor: |
| 190 | \& $hash_ref = $obj->h; # reference to whole hash |
| 191 | \& $hash_element_value = $obj->h('x'); # hash element value |
| 192 | \& $obj->h('x', 'new value'); # assign to hash element |
| 193 | .Ve |
| 194 | .PP |
| 195 | .Vb 4 |
| 196 | \& # class type accessor: |
| 197 | \& $element_value = $obj->c; # object reference |
| 198 | \& $obj->c->method(...); # call method of object |
| 199 | \& $obj->c(new My_Other_Class); # assign a new object |
| 200 | .Ve |
| 201 | .SH "DESCRIPTION" |
| 202 | .IX Header "DESCRIPTION" |
| 203 | \&\f(CW\*(C`Class::Struct\*(C'\fR exports a single function, \f(CW\*(C`struct\*(C'\fR. |
| 204 | Given a list of element names and types, and optionally |
| 205 | a class name, \f(CW\*(C`struct\*(C'\fR creates a Perl 5 class that implements |
| 206 | a \*(L"struct\-like\*(R" data structure. |
| 207 | .PP |
| 208 | The new class is given a constructor method, \f(CW\*(C`new\*(C'\fR, for creating |
| 209 | struct objects. |
| 210 | .PP |
| 211 | Each element in the struct data has an accessor method, which is |
| 212 | used to assign to the element and to fetch its value. The |
| 213 | default accessor can be overridden by declaring a \f(CW\*(C`sub\*(C'\fR of the |
| 214 | same name in the package. (See Example 2.) |
| 215 | .PP |
| 216 | Each element's type can be scalar, array, hash, or class. |
| 217 | .ie n .Sh "The ""struct()"" function" |
| 218 | .el .Sh "The \f(CWstruct()\fP function" |
| 219 | .IX Subsection "The struct() function" |
| 220 | The \f(CW\*(C`struct\*(C'\fR function has three forms of parameter\-list. |
| 221 | .PP |
| 222 | .Vb 3 |
| 223 | \& struct( CLASS_NAME => [ ELEMENT_LIST ]); |
| 224 | \& struct( CLASS_NAME => { ELEMENT_LIST }); |
| 225 | \& struct( ELEMENT_LIST ); |
| 226 | .Ve |
| 227 | .PP |
| 228 | The first and second forms explicitly identify the name of the |
| 229 | class being created. The third form assumes the current package |
| 230 | name as the class name. |
| 231 | .PP |
| 232 | An object of a class created by the first and third forms is |
| 233 | based on an array, whereas an object of a class created by the |
| 234 | second form is based on a hash. The array-based forms will be |
| 235 | somewhat faster and smaller; the hash-based forms are more |
| 236 | flexible. |
| 237 | .PP |
| 238 | The class created by \f(CW\*(C`struct\*(C'\fR must not be a subclass of another |
| 239 | class other than \f(CW\*(C`UNIVERSAL\*(C'\fR. |
| 240 | .PP |
| 241 | It can, however, be used as a superclass for other classes. To facilitate |
| 242 | this, the generated constructor method uses a two-argument blessing. |
| 243 | Furthermore, if the class is hash\-based, the key of each element is |
| 244 | prefixed with the class name (see \fIPerl Cookbook\fR, Recipe 13.12). |
| 245 | .PP |
| 246 | A function named \f(CW\*(C`new\*(C'\fR must not be explicitly defined in a class |
| 247 | created by \f(CW\*(C`struct\*(C'\fR. |
| 248 | .PP |
| 249 | The \fI\s-1ELEMENT_LIST\s0\fR has the form |
| 250 | .PP |
| 251 | .Vb 1 |
| 252 | \& NAME => TYPE, ... |
| 253 | .Ve |
| 254 | .PP |
| 255 | Each name-type pair declares one element of the struct. Each |
| 256 | element name will be defined as an accessor method unless a |
| 257 | method by that name is explicitly defined; in the latter case, a |
| 258 | warning is issued if the warning flag (\fB\-w\fR) is set. |
| 259 | .Sh "Class Creation at Compile Time" |
| 260 | .IX Subsection "Class Creation at Compile Time" |
| 261 | \&\f(CW\*(C`Class::Struct\*(C'\fR can create your class at compile time. The main reason |
| 262 | for doing this is obvious, so your class acts like every other class in |
| 263 | Perl. Creating your class at compile time will make the order of events |
| 264 | similar to using any other class ( or Perl module ). |
| 265 | .PP |
| 266 | There is no significant speed gain between compile time and run time |
| 267 | class creation, there is just a new, more standard order of events. |
| 268 | .Sh "Element Types and Accessor Methods" |
| 269 | .IX Subsection "Element Types and Accessor Methods" |
| 270 | The four element types \*(-- scalar, array, hash, and class \*(-- are |
| 271 | represented by strings \*(-- \f(CW'$'\fR, \f(CW'@'\fR, \f(CW'%'\fR, and a class name \*(-- |
| 272 | optionally preceded by a \f(CW'*'\fR. |
| 273 | .PP |
| 274 | The accessor method provided by \f(CW\*(C`struct\*(C'\fR for an element depends |
| 275 | on the declared type of the element. |
| 276 | .ie n .IP "Scalar ('$'\fR or \f(CW'*$')" 4 |
| 277 | .el .IP "Scalar (\f(CW'$'\fR or \f(CW'*$'\fR)" 4 |
| 278 | .IX Item "Scalar ('$' or '*$')" |
| 279 | The element is a scalar, and by default is initialized to \f(CW\*(C`undef\*(C'\fR |
| 280 | (but see \*(L"Initializing with new\*(R"). |
| 281 | .Sp |
| 282 | The accessor's argument, if any, is assigned to the element. |
| 283 | .Sp |
| 284 | If the element type is \f(CW'$'\fR, the value of the element (after |
| 285 | assignment) is returned. If the element type is \f(CW'*$'\fR, a reference |
| 286 | to the element is returned. |
| 287 | .ie n .IP "Array ('@'\fR or \f(CW'*@')" 4 |
| 288 | .el .IP "Array (\f(CW'@'\fR or \f(CW'*@'\fR)" 4 |
| 289 | .IX Item "Array ('@' or '*@')" |
| 290 | The element is an array, initialized by default to \f(CW\*(C`()\*(C'\fR. |
| 291 | .Sp |
| 292 | With no argument, the accessor returns a reference to the |
| 293 | element's whole array (whether or not the element was |
| 294 | specified as \f(CW'@'\fR or \f(CW'*@'\fR). |
| 295 | .Sp |
| 296 | With one or two arguments, the first argument is an index |
| 297 | specifying one element of the array; the second argument, if |
| 298 | present, is assigned to the array element. If the element type |
| 299 | is \f(CW'@'\fR, the accessor returns the array element value. If the |
| 300 | element type is \f(CW'*@'\fR, a reference to the array element is |
| 301 | returned. |
| 302 | .Sp |
| 303 | As a special case, when the accessor is called with an array reference |
| 304 | as the sole argument, this causes an assignment of the whole array element. |
| 305 | The object reference is returned. |
| 306 | .ie n .IP "Hash ('%'\fR or \f(CW'*%')" 4 |
| 307 | .el .IP "Hash (\f(CW'%'\fR or \f(CW'*%'\fR)" 4 |
| 308 | .IX Item "Hash ('%' or '*%')" |
| 309 | The element is a hash, initialized by default to \f(CW\*(C`()\*(C'\fR. |
| 310 | .Sp |
| 311 | With no argument, the accessor returns a reference to the |
| 312 | element's whole hash (whether or not the element was |
| 313 | specified as \f(CW'%'\fR or \f(CW'*%'\fR). |
| 314 | .Sp |
| 315 | With one or two arguments, the first argument is a key specifying |
| 316 | one element of the hash; the second argument, if present, is |
| 317 | assigned to the hash element. If the element type is \f(CW'%'\fR, the |
| 318 | accessor returns the hash element value. If the element type is |
| 319 | \&\f(CW'*%'\fR, a reference to the hash element is returned. |
| 320 | .Sp |
| 321 | As a special case, when the accessor is called with a hash reference |
| 322 | as the sole argument, this causes an assignment of the whole hash element. |
| 323 | The object reference is returned. |
| 324 | .ie n .IP "Class ('Class_Name'\fR or \f(CW'*Class_Name')" 4 |
| 325 | .el .IP "Class (\f(CW'Class_Name'\fR or \f(CW'*Class_Name'\fR)" 4 |
| 326 | .IX Item "Class ('Class_Name' or '*Class_Name')" |
| 327 | The element's value must be a reference blessed to the named |
| 328 | class or to one of its subclasses. The element is not initialized |
| 329 | by default. |
| 330 | .Sp |
| 331 | The accessor's argument, if any, is assigned to the element. The |
| 332 | accessor will \f(CW\*(C`croak\*(C'\fR if this is not an appropriate object |
| 333 | reference. |
| 334 | .Sp |
| 335 | If the element type does not start with a \f(CW'*'\fR, the accessor |
| 336 | returns the element value (after assignment). If the element type |
| 337 | starts with a \f(CW'*'\fR, a reference to the element itself is returned. |
| 338 | .ie n .Sh "Initializing with ""new""" |
| 339 | .el .Sh "Initializing with \f(CWnew\fP" |
| 340 | .IX Subsection "Initializing with new" |
| 341 | \&\f(CW\*(C`struct\*(C'\fR always creates a constructor called \f(CW\*(C`new\*(C'\fR. That constructor |
| 342 | may take a list of initializers for the various elements of the new |
| 343 | struct. |
| 344 | .PP |
| 345 | Each initializer is a pair of values: \fIelement name\fR\f(CW\*(C` => \*(C'\fR\fIvalue\fR. |
| 346 | The initializer value for a scalar element is just a scalar value. The |
| 347 | initializer for an array element is an array reference. The initializer |
| 348 | for a hash is a hash reference. |
| 349 | .PP |
| 350 | The initializer for a class element is an object of the corresponding class, |
| 351 | or of one of it's subclasses, or a reference to a hash containing named |
| 352 | arguments to be passed to the element's constructor. |
| 353 | .PP |
| 354 | See Example 3 below for an example of initialization. |
| 355 | .SH "EXAMPLES" |
| 356 | .IX Header "EXAMPLES" |
| 357 | .IP "Example 1" 4 |
| 358 | .IX Item "Example 1" |
| 359 | Giving a struct element a class type that is also a struct is how |
| 360 | structs are nested. Here, \f(CW\*(C`Timeval\*(C'\fR represents a time (seconds and |
| 361 | microseconds), and \f(CW\*(C`Rusage\*(C'\fR has two elements, each of which is of |
| 362 | type \f(CW\*(C`Timeval\*(C'\fR. |
| 363 | .Sp |
| 364 | .Vb 1 |
| 365 | \& use Class::Struct; |
| 366 | .Ve |
| 367 | .Sp |
| 368 | .Vb 4 |
| 369 | \& struct( Rusage => { |
| 370 | \& ru_utime => 'Timeval', # user time used |
| 371 | \& ru_stime => 'Timeval', # system time used |
| 372 | \& }); |
| 373 | .Ve |
| 374 | .Sp |
| 375 | .Vb 4 |
| 376 | \& struct( Timeval => [ |
| 377 | \& tv_secs => '$', # seconds |
| 378 | \& tv_usecs => '$', # microseconds |
| 379 | \& ]); |
| 380 | .Ve |
| 381 | .Sp |
| 382 | .Vb 2 |
| 383 | \& # create an object: |
| 384 | \& my $t = Rusage->new(ru_utime=>Timeval->new(), ru_stime=>Timeval->new()); |
| 385 | .Ve |
| 386 | .Sp |
| 387 | .Vb 6 |
| 388 | \& # $t->ru_utime and $t->ru_stime are objects of type Timeval. |
| 389 | \& # set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec. |
| 390 | \& $t->ru_utime->tv_secs(100); |
| 391 | \& $t->ru_utime->tv_usecs(0); |
| 392 | \& $t->ru_stime->tv_secs(5); |
| 393 | \& $t->ru_stime->tv_usecs(0); |
| 394 | .Ve |
| 395 | .IP "Example 2" 4 |
| 396 | .IX Item "Example 2" |
| 397 | An accessor function can be redefined in order to provide |
| 398 | additional checking of values, etc. Here, we want the \f(CW\*(C`count\*(C'\fR |
| 399 | element always to be nonnegative, so we redefine the \f(CW\*(C`count\*(C'\fR |
| 400 | accessor accordingly. |
| 401 | .Sp |
| 402 | .Vb 2 |
| 403 | \& package MyObj; |
| 404 | \& use Class::Struct; |
| 405 | .Ve |
| 406 | .Sp |
| 407 | .Vb 2 |
| 408 | \& # declare the struct |
| 409 | \& struct ( 'MyObj', { count => '$', stuff => '%' } ); |
| 410 | .Ve |
| 411 | .Sp |
| 412 | .Vb 10 |
| 413 | \& # override the default accessor method for 'count' |
| 414 | \& sub count { |
| 415 | \& my $self = shift; |
| 416 | \& if ( @_ ) { |
| 417 | \& die 'count must be nonnegative' if $_[0] < 0; |
| 418 | \& $self->{'MyObj::count'} = shift; |
| 419 | \& warn "Too many args to count" if @_; |
| 420 | \& } |
| 421 | \& return $self->{'MyObj::count'}; |
| 422 | \& } |
| 423 | .Ve |
| 424 | .Sp |
| 425 | .Vb 4 |
| 426 | \& package main; |
| 427 | \& $x = new MyObj; |
| 428 | \& print "\e$x->count(5) = ", $x->count(5), "\en"; |
| 429 | \& # prints '$x->count(5) = 5' |
| 430 | .Ve |
| 431 | .Sp |
| 432 | .Vb 2 |
| 433 | \& print "\e$x->count = ", $x->count, "\en"; |
| 434 | \& # prints '$x->count = 5' |
| 435 | .Ve |
| 436 | .Sp |
| 437 | .Vb 2 |
| 438 | \& print "\e$x->count(-5) = ", $x->count(-5), "\en"; |
| 439 | \& # dies due to negative argument! |
| 440 | .Ve |
| 441 | .IP "Example 3" 4 |
| 442 | .IX Item "Example 3" |
| 443 | The constructor of a generated class can be passed a list |
| 444 | of \fIelement\fR=>\fIvalue\fR pairs, with which to initialize the struct. |
| 445 | If no initializer is specified for a particular element, its default |
| 446 | initialization is performed instead. Initializers for non-existent |
| 447 | elements are silently ignored. |
| 448 | .Sp |
| 449 | Note that the initializer for a nested class may be specified as |
| 450 | an object of that class, or as a reference to a hash of initializers |
| 451 | that are passed on to the nested struct's constructor. |
| 452 | .Sp |
| 453 | .Vb 1 |
| 454 | \& use Class::Struct; |
| 455 | .Ve |
| 456 | .Sp |
| 457 | .Vb 5 |
| 458 | \& struct Breed => |
| 459 | \& { |
| 460 | \& name => '$', |
| 461 | \& cross => '$', |
| 462 | \& }; |
| 463 | .Ve |
| 464 | .Sp |
| 465 | .Vb 7 |
| 466 | \& struct Cat => |
| 467 | \& [ |
| 468 | \& name => '$', |
| 469 | \& kittens => '@', |
| 470 | \& markings => '%', |
| 471 | \& breed => 'Breed', |
| 472 | \& ]; |
| 473 | .Ve |
| 474 | .Sp |
| 475 | .Vb 6 |
| 476 | \& my $cat = Cat->new( name => 'Socks', |
| 477 | \& kittens => ['Monica', 'Kenneth'], |
| 478 | \& markings => { socks=>1, blaze=>"white" }, |
| 479 | \& breed => Breed->new(name=>'short-hair', cross=>1), |
| 480 | \& or: breed => {name=>'short-hair', cross=>1}, |
| 481 | \& ); |
| 482 | .Ve |
| 483 | .Sp |
| 484 | .Vb 3 |
| 485 | \& print "Once a cat called ", $cat->name, "\en"; |
| 486 | \& print "(which was a ", $cat->breed->name, ")\en"; |
| 487 | \& print "had two kittens: ", join(' and ', @{$cat->kittens}), "\en"; |
| 488 | .Ve |
| 489 | .SH "Author and Modification History" |
| 490 | .IX Header "Author and Modification History" |
| 491 | Modified by Damian Conway, 2001\-09\-10, v0.62. |
| 492 | .PP |
| 493 | .Vb 11 |
| 494 | \& Modified implicit construction of nested objects. |
| 495 | \& Now will also take an object ref instead of requiring a hash ref. |
| 496 | \& Also default initializes nested object attributes to undef, rather |
| 497 | \& than calling object constructor without args |
| 498 | \& Original over-helpfulness was fraught with problems: |
| 499 | \& * the class's constructor might not be called 'new' |
| 500 | \& * the class might not have a hash-like-arguments constructor |
| 501 | \& * the class might not have a no-argument constructor |
| 502 | \& * "recursive" data structures didn't work well: |
| 503 | \& package Person; |
| 504 | \& struct { mother => 'Person', father => 'Person'}; |
| 505 | .Ve |
| 506 | .PP |
| 507 | Modified by Casey West, 2000\-11\-08, v0.59. |
| 508 | .PP |
| 509 | .Vb 1 |
| 510 | \& Added the ability for compile time class creation. |
| 511 | .Ve |
| 512 | .PP |
| 513 | Modified by Damian Conway, 1999\-03\-05, v0.58. |
| 514 | .PP |
| 515 | .Vb 1 |
| 516 | \& Added handling of hash-like arg list to class ctor. |
| 517 | .Ve |
| 518 | .PP |
| 519 | .Vb 2 |
| 520 | \& Changed to two-argument blessing in ctor to support |
| 521 | \& derivation from created classes. |
| 522 | .Ve |
| 523 | .PP |
| 524 | .Vb 2 |
| 525 | \& Added classname prefixes to keys in hash-based classes |
| 526 | \& (refer to "Perl Cookbook", Recipe 13.12 for rationale). |
| 527 | .Ve |
| 528 | .PP |
| 529 | .Vb 5 |
| 530 | \& Corrected behaviour of accessors for '*@' and '*%' struct |
| 531 | \& elements. Package now implements documented behaviour when |
| 532 | \& returning a reference to an entire hash or array element. |
| 533 | \& Previously these were returned as a reference to a reference |
| 534 | \& to the element. |
| 535 | .Ve |
| 536 | .PP |
| 537 | Renamed to \f(CW\*(C`Class::Struct\*(C'\fR and modified by Jim Miner, 1997\-04\-02. |
| 538 | .PP |
| 539 | .Vb 8 |
| 540 | \& members() function removed. |
| 541 | \& Documentation corrected and extended. |
| 542 | \& Use of struct() in a subclass prohibited. |
| 543 | \& User definition of accessor allowed. |
| 544 | \& Treatment of '*' in element types corrected. |
| 545 | \& Treatment of classes as element types corrected. |
| 546 | \& Class name to struct() made optional. |
| 547 | \& Diagnostic checks added. |
| 548 | .Ve |
| 549 | .PP |
| 550 | Originally \f(CW\*(C`Class::Template\*(C'\fR by Dean Roehrich. |
| 551 | .PP |
| 552 | .Vb 19 |
| 553 | \& # Template.pm --- struct/member template builder |
| 554 | \& # 12mar95 |
| 555 | \& # Dean Roehrich |
| 556 | \& # |
| 557 | \& # changes/bugs fixed since 28nov94 version: |
| 558 | \& # - podified |
| 559 | \& # changes/bugs fixed since 21nov94 version: |
| 560 | \& # - Fixed examples. |
| 561 | \& # changes/bugs fixed since 02sep94 version: |
| 562 | \& # - Moved to Class::Template. |
| 563 | \& # changes/bugs fixed since 20feb94 version: |
| 564 | \& # - Updated to be a more proper module. |
| 565 | \& # - Added "use strict". |
| 566 | \& # - Bug in build_methods, was using @var when @$var needed. |
| 567 | \& # - Now using my() rather than local(). |
| 568 | \& # |
| 569 | \& # Uses perl5 classes to create nested data types. |
| 570 | \& # This is offered as one implementation of Tom Christiansen's "structs.pl" |
| 571 | \& # idea. |
| 572 | .Ve |