docs/latex/wx/variant.tex

   1 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
   2 %% Name:        variant.tex
   3 %% Purpose:     wxVariant docs
   4 %% Author:      wxWidgets Team
   5 %% Modified by:
   6 %% Created:     01/30/2005
   7 %% RCS-ID:      $Id$
   8 %% Copyright:   (c) wxWidgets Team
   9 %% License:     wxWindows license
  10 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  11
  12 \section{\class{wxVariant}}\label{wxvariant}
  13
  14 The {\bf wxVariant} class represents a container for any type.
  15 A variant's value can be changed at run time, possibly to a different type of value.
  16
  17 As standard, wxVariant can store values of type bool, wxChar, double, long, string,
  18 string list, time, date, void pointer, list of strings, and list of variants.
  19 However, an application can extend wxVariant's capabilities by deriving from the
  20 class \helpref{wxVariantData}{wxvariantdata} and using the wxVariantData form of
  21 the wxVariant constructor or assignment operator to assign this data to a variant.
  22 Actual values for user-defined types will need to be accessed via the wxVariantData
  23 object, unlike the case for basic data types where convenience functions such as
  24 \helpref{GetLong}{wxvariantgetlong} can be used.
  25
  26 Pointers to any \helpref{wxObject}{wxobject} derived class can also easily be stored
  27 in a wxVariant. wxVariant will then use wxWidgets' built-in RTTI system to set the
  28 type name (returned by \helpref{GetType}{wxvariantgettype}) and to perform
  29 type-safety checks at runtime.
  30
  31 This class is useful for reducing the programming for certain tasks, such as an editor
  32 for different data types, or a remote procedure call protocol.
  33
  34 An optional name member is associated with a wxVariant. This might be used, for example,
  35 in CORBA or OLE automation classes, where named parameters are required.
  36
  37 Note that as of wxWidgets 2.7.1, wxVariant is \helpref{reference counted}{trefcount}.
  38 Additionally, the convenience macros {\bf DECLARE\_VARIANT\_OBJECT} and
  39 {\bf IMPLEMENT\_VARIANT\_OBJECT} were added so that adding (limited) support
  40 for conversion to and from wxVariant can be very easily implemented without modifying
  41 either wxVariant or the class to be stored by wxVariant. Since assignment operators
  42 cannot be declared outside the class, the shift left operators are used like this:
  43
  44 \begin{verbatim}
  45     // in the header file
  46     DECLARE_VARIANT_OBJECT(MyClass)
  47
  48     // in the implementation file
  49     IMPLMENT_VARIANT_OBJECT(MyClass)
  50
  51     // in the user code
  52     wxVariant variant;
  53     MyClass value;
  54     variant << value;
  55
  56     // or
  57     value << variant;
  58 \end{verbatim}
  59
  60 For this to work, MyClass must derive from \helpref{wxObject}{wxobject}, implement
  61 the \helpref{wxWidgets RTTI system}{runtimeclassoverview}
  62 and support the assignment operator and equality operator for itself. Ideally, it
  63 should also be reference counted to make copying operations cheap and fast. This
  64 can be most easily implemented using the reference counting support offered by
  65 \helpref{wxObject}{wxobject} itself. By default, wxWidgets already implements
  66 the shift operator conversion for a few of its drawing related classes:
  67
  68 \begin{verbatim}
  69 IMPLEMENT_VARIANT_OBJECT(wxColour)
  70 IMPLEMENT_VARIANT_OBJECT(wxImage)
  71 IMPLEMENT_VARIANT_OBJECT(wxIcon)
  72 IMPLEMENT_VARIANT_OBJECT(wxBitmap)
  73 \end{verbatim}
  74
  75 \wxheading{Derived from}
  76
  77 \helpref{wxObject}{wxobject}
  78
  79 \wxheading{Include files}
  80
  81 <wx/variant.h>
  82
  83 \wxheading{Library}
  84
  85 \helpref{wxBase}{librarieslist}
  86
  87 \wxheading{See also}
  88
  89 \helpref{wxVariantData}{wxvariantdata}
  90
  91 \latexignore{\rtfignore{\wxheading{Members}}}
  92
  93 \membersection{wxVariant::wxVariant}\label{wxvariantctor}
  94
  95 \func{}{wxVariant}{\void}
  96
  97 Default constructor.
  98
  99 \func{}{wxVariant}{\param{const wxVariant\& }{variant}}
 100
 101 Copy constructor, uses \helpref{reference counting}{trefcount}.
 102
 103 \func{}{wxVariant}{\param{const wxChar*}{ value}, \param{const wxString\& }{name = ``"}}
 104
 105 \func{}{wxVariant}{\param{const wxString\&}{ value}, \param{const wxString\& }{name = ``"}}
 106
 107 Construction from a string value.
 108
 109 \func{}{wxVariant}{\param{wxChar}{ value}, \param{const wxString\& }{name = ``"}}
 110
 111 Construction from a character value.
 112
 113 \func{}{wxVariant}{\param{long}{ value}, \param{const wxString\& }{name = ``"}}
 114
 115 Construction from an integer value. You may need to cast to (long) to
 116 avoid confusion with other constructors (such as the bool constructor).
 117
 118 \func{}{wxVariant}{\param{bool}{ value}, \param{const wxString\& }{name = ``"}}
 119
 120 Construction from a boolean value.
 121
 122 \func{}{wxVariant}{\param{double}{ value}, \param{const wxString\& }{name = ``"}}
 123
 124 Construction from a double-precision floating point value.
 125
 126 \func{}{wxVariant}{\param{const wxList\&}{ value}, \param{const wxString\& }{name = ``"}}
 127
 128 Construction from a list of wxVariant objects. This constructor
 129 copies {\it value}, the application is still responsible for
 130 deleting {\it value} and its contents.
 131
 132 \func{}{wxVariant}{\param{void*}{ value}, \param{const wxString\& }{name = ``"}}
 133
 134 Construction from a void pointer.
 135
 136 \func{}{wxVariant}{\param{wxObject*}{ value}, \param{const wxString\& }{name = ``"}}
 137
 138 Construction from a wxObject pointer.
 139
 140 \func{}{wxVariant}{\param{wxVariantData*}{ data}, \param{const wxString\& }{name = ``"}}
 141
 142 Construction from user-defined data.  The variant holds onto the {\it data} pointer.
 143
 144 \func{}{wxVariant}{\param{wxDateTime\&}{ val}, \param{const wxString\& }{name = ``"}}
 145
 146 Construction from a \helpref{wxDateTime}{wxdatetime}.
 147
 148 \func{}{wxVariant}{\param{wxArrayString\&}{ val}, \param{const wxString\& }{name = ``"}}
 149
 150 Construction from an array of strings.  This constructor copies {\it value} and its contents.
 151
 152 \func{}{wxVariant}{\param{DATE\_STRUCT*}{ val}, \param{const wxString\& }{name = ``"}}
 153
 154 Construction from a odbc date value.  Represented internally by a \helpref{wxDateTime}{wxdatetime} value.
 155
 156 \func{}{wxVariant}{\param{TIME\_STRUCT*}{ val}, \param{const wxString\& }{name = ``"}}
 157
 158 Construction from a odbc time value.  Represented internally by a \helpref{wxDateTime}{wxdatetime} value.
 159
 160 \func{}{wxVariant}{\param{TIMESTAMP\_STRUCT*}{ val}, \param{const wxString\& }{name = ``"}}
 161
 162 Construction from a odbc timestamp value.  Represented internally by a \helpref{wxDateTime}{wxdatetime} value.
 163
 164 \membersection{wxVariant::\destruct{wxVariant}}\label{wxvariantdtor}
 165
 166 \func{}{\destruct{wxVariant}}{\void}
 167
 168 Destructor.
 169
 170 Note that destructor is protected, so wxVariantData cannot usually
 171 be deleted. Instead, \helpref{DecRef}{wxvariantdatadecref} should be called.
 172 See \helpref{reference-counted object destruction}{refcountdestruct} for more info.
 173
 174
 175 \membersection{wxVariant::Append}\label{wxvariantappend}
 176
 177 \func{void}{Append}{\param{const wxVariant\&}{ value}}
 178
 179 Appends a value to the list.
 180
 181 \membersection{wxVariant::Clear}\label{wxvariantclear}
 182
 183 \func{void}{Clear}{\void}
 184
 185 Makes the variant null by deleting the internal data and
 186 set the name to {\it wxEmptyString}.
 187
 188 \membersection{wxVariant::ClearList}\label{wxvariantclearlist}
 189
 190 \func{void}{ClearList}{\void}
 191
 192 Deletes the contents of the list.
 193
 194
 195 \membersection{wxVariant::Convert}\label{wxvariantconvert}
 196
 197 \constfunc{bool}{Convert}{\param{long*}{ value}}
 198
 199 \constfunc{bool}{Convert}{\param{bool*}{ value}}
 200
 201 \constfunc{bool}{Convert}{\param{double*}{ value}}
 202
 203 \constfunc{bool}{Convert}{\param{wxString*}{ value}}
 204
 205 \constfunc{bool}{Convert}{\param{wxChar*}{ value}}
 206
 207 \constfunc{bool}{Convert}{\param{wxDateTime*}{ value}}
 208
 209 Retrieves and converts the value of this variant to the type that {\it value} is.
 210
 211
 212 \membersection{wxVariant::GetCount}\label{wxvariantgetcount}
 213
 214 \constfunc{size\_t}{GetCount}{\void}
 215
 216 Returns the number of elements in the list.
 217
 218 \membersection{wxVariant::Delete}\label{wxvariantdelete}
 219
 220 \func{bool}{Delete}{\param{size\_t }{item}}
 221
 222 Deletes the zero-based {\it item} from the list.
 223
 224 \membersection{wxVariant::GetArrayString}\label{wxvariantgetarraystring}
 225
 226 \constfunc{wxArrayString}{GetArrayString}{\void}
 227
 228 Returns the string array value.
 229
 230 \membersection{wxVariant::GetBool}\label{wxvariantgetbool}
 231
 232 \constfunc{bool}{GetBool}{\void}
 233
 234 Returns the boolean value.
 235
 236 \membersection{wxVariant::GetChar}\label{wxvariantgetchar}
 237
 238 \constfunc{wxChar}{GetChar}{\void}
 239
 240 Returns the character value.
 241
 242 \membersection{wxVariant::GetData}\label{wxvariantgetdata}
 243
 244 \constfunc{wxVariantData*}{GetData}{\void}
 245
 246 Returns a pointer to the internal variant data. To take ownership
 247 of this data, you must call its \helpref{IncRef}{wxvariantdataincref}
 248 method. When you stop using it, \helpref{DecRef}{wxvariantdatadecref}
 249 must be likewise called.
 250
 251 \membersection{wxVariant::GetDateTime}\label{wxvariantgetdatetime}
 252
 253 \constfunc{wxDateTime}{GetDateTime}{\void}
 254
 255 Returns the date value.
 256
 257 \membersection{wxVariant::GetDouble}\label{wxvariantgetdouble}
 258
 259 \constfunc{double}{GetDouble}{\void}
 260
 261 Returns the floating point value.
 262
 263 \membersection{wxVariant::GetLong}\label{wxvariantgetlong}
 264
 265 \constfunc{long}{GetLong}{\void}
 266
 267 Returns the integer value.
 268
 269 \membersection{wxVariant::GetName}\label{wxvariantgetname}
 270
 271 \constfunc{const wxString\&}{GetName}{\void}
 272
 273 Returns a constant reference to the variant name.
 274
 275 \membersection{wxVariant::GetString}\label{wxvariantgetstring}
 276
 277 \constfunc{wxString}{GetString}{\void}
 278
 279 Gets the string value.
 280
 281 \membersection{wxVariant::GetType}\label{wxvariantgettype}
 282
 283 \constfunc{wxString}{GetType}{\void}
 284
 285 Returns the value type as a string. The built-in types are: bool, char, date, double, list, long, string, stringlist, time, void*.
 286
 287 If the variant is null, the value type returned is the string ``null" (not the empty string).
 288
 289 \membersection{wxVariant::GetVoidPtr}\label{wxvariantgetvoidptr}
 290
 291 \constfunc{void*}{GetVoidPtr}{\void}
 292
 293 Gets the void pointer value.
 294
 295 \membersection{wxVariant::GetWxObjectPtr}\label{wxvariantgetwxobjectptr}
 296
 297 \constfunc{wxObject*}{GetWxObjectPtr}{\void}
 298
 299 Gets the wxObject pointer value.
 300
 301 \membersection{wxVariant::Insert}\label{wxvariantinsert}
 302
 303 \func{void}{Insert}{\param{const wxVariant\&}{ value}}
 304
 305 Inserts a value at the front of the list.
 306
 307 \membersection{wxVariant::IsNull}\label{wxvariantisnull}
 308
 309 \constfunc{bool}{IsNull}{\void}
 310
 311 Returns true if there is no data associated with this variant, false if there is data.
 312
 313 \membersection{wxVariant::IsType}\label{wxvariantistype}
 314
 315 \constfunc{bool}{IsType}{\param{const wxString\&}{ type}}
 316
 317 Returns true if {\it type} matches the type of the variant, false otherwise.
 318
 319 \membersection{wxVariant::IsValueKindOf}\label{wxvariantisvaluekindof}
 320
 321 \constfunc{bool}{IsValueKindOf}{\param{const wxClassInfo* type}{ type}}
 322
 323 Returns true if the data is derived from the class described by {\it type}, false otherwise.
 324
 325 \membersection{wxVariant::MakeNull}\label{wxvariantmakenull}
 326
 327 \func{void}{MakeNull}{\void}
 328
 329 Makes the variant null by deleting the internal data.
 330
 331 \membersection{wxVariant::MakeString}\label{wxvariantmakestring}
 332
 333 \constfunc{wxString}{MakeString}{\void}
 334
 335 Makes a string representation of the variant value (for any type).
 336
 337 \membersection{wxVariant::Member}\label{wxvariantmember}
 338
 339 \constfunc{bool}{Member}{\param{const wxVariant\&}{ value}}
 340
 341 Returns true if {\it value} matches an element in the list.
 342
 343 \membersection{wxVariant::NullList}\label{wxvariantnulllist}
 344
 345 \func{void}{NullList}{\void}
 346
 347 Makes an empty list. This differs from a null variant which has no data; a null list
 348 is of type list, but the number of elements in the list is zero.
 349
 350 \membersection{wxVariant::SetData}\label{wxvariantsetdata}
 351
 352 \func{void}{SetData}{\param{wxVariantData*}{ data}}
 353
 354 Sets the internal variant data, deleting the existing data if there is any.
 355
 356 \membersection{wxVariant::operator $=$}\label{wxvariantassignment}
 357
 358 \func{void}{operator $=$}{\param{const wxVariant\& }{value}}
 359
 360 \func{void}{operator $=$}{\param{wxVariantData* }{value}}
 361
 362 \func{void}{operator $=$}{\param{const wxString\& }{value}}
 363
 364 \func{void}{operator $=$}{\param{const wxChar* }{value}}
 365
 366 \func{void}{operator $=$}{\param{wxChar }{value}}
 367
 368 \func{void}{operator $=$}{\param{const long }{value}}
 369
 370 \func{void}{operator $=$}{\param{const bool }{value}}
 371
 372 \func{void}{operator $=$}{\param{const double }{value}}
 373
 374 \func{void}{operator $=$}{\param{void* }{value}}
 375
 376 \func{void}{operator $=$}{\param{wxObject* }{value}}
 377
 378 \func{void}{operator $=$}{\param{const wxList\& }{value}}
 379
 380 \func{void}{operator $=$}{\param{const wxDateTime\& }{value}}
 381
 382 \func{void}{operator $=$}{\param{const wxArrayString\& }{value}}
 383
 384 \func{void}{operator $=$}{\param{const DATE\_STRUCT* }{value}}
 385
 386 \func{void}{operator $=$}{\param{const TIME\_STRUCT* }{value}}
 387
 388 \func{void}{operator $=$}{\param{const TIMESTAMP\_STRUCT* }{value}}
 389
 390 Assignment operators, using \helpref{reference counting}{trefcount} when possible.
 391
 392 \membersection{wxVariant::operator $==$}\label{wxvarianteq}
 393
 394 \constfunc{bool}{operator $==$}{\param{const wxVariant\& }{value}}
 395
 396 \constfunc{bool}{operator $==$}{\param{const wxString\& }{value}}
 397
 398 \constfunc{bool}{operator $==$}{\param{const wxChar* }{value}}
 399
 400 \constfunc{bool}{operator $==$}{\param{wxChar }{value}}
 401
 402 \constfunc{bool}{operator $==$}{\param{const long }{value}}
 403
 404 \constfunc{bool}{operator $==$}{\param{const bool }{value}}
 405
 406 \constfunc{bool}{operator $==$}{\param{const double }{value}}
 407
 408 \constfunc{bool}{operator $==$}{\param{void* }{value}}
 409
 410 \constfunc{bool}{operator $==$}{\param{wxObject* }{value}}
 411
 412 \constfunc{bool}{operator $==$}{\param{const wxList\& }{value}}
 413
 414 \constfunc{bool}{operator $==$}{\param{const wxArrayString\& }{value}}
 415
 416 \constfunc{bool}{operator $==$}{\param{const wxDateTime\& }{value}}
 417
 418 Equality test operators.
 419
 420 \membersection{wxVariant::operator $!=$}\label{wxvariantneq}
 421
 422 \constfunc{bool}{operator $!=$}{\param{const wxVariant\& }{value}}
 423
 424 \constfunc{bool}{operator $!=$}{\param{const wxString\& }{value}}
 425
 426 \constfunc{bool}{operator $!=$}{\param{const wxChar* }{value}}
 427
 428 \constfunc{bool}{operator $!=$}{\param{wxChar }{value}}
 429
 430 \constfunc{bool}{operator $!=$}{\param{const long }{value}}
 431
 432 \constfunc{bool}{operator $!=$}{\param{const bool }{value}}
 433
 434 \constfunc{bool}{operator $!=$}{\param{const double }{value}}
 435
 436 \constfunc{bool}{operator $!=$}{\param{void* }{value}}
 437
 438 \constfunc{bool}{operator $!=$}{\param{wxObject* }{value}}
 439
 440 \constfunc{bool}{operator $!=$}{\param{const wxList\& }{value}}
 441
 442 \constfunc{bool}{operator $!=$}{\param{const wxArrayString\& }{value}}
 443
 444 \constfunc{bool}{operator $!=$}{\param{const wxDateTime\& }{value}}
 445
 446 Inequality test operators.
 447
 448 \membersection{wxVariant::operator $[]$}\label{wxvariantarray}
 449
 450 \constfunc{wxVariant}{operator $[]$}{\param{size\_t }{idx}}
 451
 452 Returns the value at {\it idx} (zero-based).
 453
 454 \func{wxVariant\&}{operator $[]$}{\param{size\_t }{idx}}
 455
 456 Returns a reference to the value at {\it idx} (zero-based). This can be used
 457 to change the value at this index.
 458
 459 \membersection{wxVariant::operator wxChar}\label{wxvariantchar}
 460
 461 \constfunc{char}{operator wxChar}{\void}
 462
 463 Operator for implicit conversion to a wxChar, using \helpref{wxVariant::GetChar}{wxvariantgetchar}.
 464
 465 \membersection{wxVariant::operator double}\label{wxvariantdouble}
 466
 467 \constfunc{double}{operator double}{\void}
 468
 469 Operator for implicit conversion to a double, using \helpref{wxVariant::GetDouble}{wxvariantgetdouble}.
 470
 471 \constfunc{long}{operator long}{\void}
 472
 473 Operator for implicit conversion to a long, using \helpref{wxVariant::GetLong}{wxvariantgetlong}.
 474
 475 \membersection{wxVariant::operator wxString}\label{wxvariantwxstring}
 476
 477 \constfunc{wxString}{operator wxString}{\void}
 478
 479 Operator for implicit conversion to a string, using \helpref{wxVariant::MakeString}{wxvariantmakestring}.
 480
 481 \membersection{wxVariant::operator void*}\label{wxvariantvoid}
 482
 483 \constfunc{void*}{operator void*}{\void}
 484
 485 Operator for implicit conversion to a pointer to a void, using \helpref{wxVariant::GetVoidPtr}{wxvariantgetvoidptr}.
 486
 487 \membersection{wxVariant::operator wxDateTime}\label{wxvariantdatetime}
 488
 489 \constfunc{void*}{operator wxDateTime}{\void}
 490
 491 Operator for implicit conversion to a pointer to a \helpref{wxDateTime}{wxdatetime}, using \helpref{wxVariant::GetDateTime}{wxvariantgetdatetime}.
 492
 493
 494
 495 %% wxVariantData
 496
 497
 498 \section{\class{wxVariantData}}\label{wxvariantdata}
 499
 500 The {\bf wxVariantData} class is used to implement a new type for \helpref{wxVariant}{wxvariant}.
 501 Derive from wxVariantData, and override the pure virtual functions.
 502
 503 wxVariantData is \helpref{reference counted}{refcount}, but you don't normally have to care about this,
 504 as wxVariant manages the count automatically. However, in case your application needs to take
 505 ownership of wxVariantData, be aware that the object is created with reference count of 1,
 506 and passing it to wxVariant will not increase this. In other words, \helpref{IncRef}{wxvariantdataincref}
 507 needs to be called only if you both take ownership of wxVariantData and pass it to a wxVariant.
 508 Also note that the destructor is protected, so you can never explicitly delete a wxVariantData
 509 instance. Instead, \helpref{DecRef}{wxvariantdatadecref} will delete the object automatically
 510 when the reference count reaches zero.
 511
 512 \wxheading{Derived from}
 513
 514 \helpref{wxObject}{wxobject}
 515
 516 \wxheading{Include files}
 517
 518 <wx/variant.h>
 519
 520 \wxheading{Library}
 521
 522 \helpref{wxBase}{librarieslist}
 523
 524 \wxheading{See also}
 525
 526 \helpref{wxVariant}{wxvariant}
 527
 528 \latexignore{\rtfignore{\wxheading{Members}}}
 529
 530 \membersection{wxVariantData::wxVariantData}\label{wxvariantdatactor}
 531
 532 \func{}{wxVariantData}{\void}
 533
 534 Default constructor.
 535
 536 \membersection{wxVariantData::DecRef}\label{wxvariantdatadecref}
 537
 538 \func{void}{DecRef}{\void}
 539
 540 Decreases reference count. If the count reaches zero, the object is
 541 automatically deleted.
 542
 543 Note that destructor of wxVariantData is protected, so delete
 544 cannot be used as normal. Instead, \helpref{DecRef}{wxvariantdatadecref} should be called.
 545
 546
 547
 548 \membersection{wxVariantData::Eq}\label{wxvariantdataeq}
 549
 550 \constfunc{bool}{Eq}{\param{wxVariantData\&}{ data}}
 551
 552 Returns true if this object is equal to {\it data}.
 553
 554 \membersection{wxVariantData::GetType}\label{wxvariantdatagettype}
 555
 556 \constfunc{wxString}{GetType}{\void}
 557
 558 Returns the string type of the data.
 559
 560 \membersection{wxVariantData::GetValueClassInfo}\label{wxvariantdatagetvalueclassinfo}
 561
 562 \constfunc{wxClassInfo*}{GetValueClassInfo}{\void}
 563
 564 If the data is a wxObject returns a pointer to the objects wxClassInfo structure, if
 565 the data isn't a wxObject the method returns NULL.
 566
 567 \membersection{wxVariantData::IncRef}\label{wxvariantdataincref}
 568
 569 \func{void}{IncRef}{\void}
 570
 571 Increases reference count. Note that initially wxVariantData has reference count of 1.
 572
 573 \membersection{wxVariantData::Read}\label{wxvariantdataread}
 574
 575 \func{bool}{Read}{\param{ostream\&}{ stream}}
 576
 577 \func{bool}{Read}{\param{wxString\&}{ string}}
 578
 579 Reads the data from {\it stream} or {\it string}.
 580
 581 \membersection{wxVariantData::Write}\label{wxvariantdatawrite}
 582
 583 \constfunc{bool}{Write}{\param{ostream\&}{ stream}}
 584
 585 \constfunc{bool}{Write}{\param{wxString\&}{ string}}
 586
 587 Writes the data to {\it stream} or {\it string}.
 588
 589
 590 \membersection{wxGetVariantCast}\label{wxgetvariantcast}
 591
 592 \func{classname *}{wxGetVariantCast}{wxVariant\&, classname}
 593
 594 This macro returns the data stored in {\it variant} cast to the type {\it classname *} if
 595 the data is of this type (the check is done during the run-time) or
 596 {\tt NULL} otherwise.
 597
 598
 599 \wxheading{See also}
 600
 601 \helpref{RTTI overview}{runtimeclassoverview}\\
 602 \helpref{wxDynamicCast}{wxdynamiccast}
 603