docs/doxygen/overviews/container.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        container.h
   3 // Purpose:     topic overview
   4 // Author:      wxWidgets team
   5 // RCS-ID:      $Id$
   6 // Licence:     wxWindows license
   7 /////////////////////////////////////////////////////////////////////////////
   8
   9 /*!
  10
  11  @page overview_container Container classes overview
  12
  13  Classes: #wxListT, #wxArrayT, #wxVectorT
  14
  15  wxWidgets uses itself several container classes including doubly-linked lists
  16  and dynamic arrays (i.e. arrays which expand automatically when they become
  17  full). For both historical and portability reasons wxWidgets does not use STL
  18  which provides the standard implementation of many container classes in C++.
  19
  20  First of all, wxWidgets has existed since well before STL was written, and
  21  secondly we don't believe that today compilers can deal really well with all of
  22  STL classes (this is especially true for some less common platforms). Of
  23  course, the compilers are evolving quite rapidly and hopefully their progress
  24  will allow to base future versions of wxWidgets on STL - but this is not yet
  25  the case.
  26
  27  wxWidgets container classes don't pretend to be as powerful or full as STL
  28  ones, but they are quite useful and may be compiled with absolutely any C++
  29  compiler. They're used internally by wxWidgets, but may, of course, be used in
  30  your programs as well if you wish.
  31
  32  The list classes in wxWidgets are doubly-linked lists which may either own the
  33  objects they contain (meaning that the list deletes the object when it is
  34  removed from the list or the list itself is destroyed) or just store the
  35  pointers depending on whether you called or not wxList::DeleteContents method.
  36
  37  Dynamic arrays resemble C arrays but with two important differences: they
  38  provide run-time range checking in debug builds and they automatically expand
  39  the allocated memory when there is no more space for new items. They come in
  40  two sorts: the "plain" arrays which store either built-in types such as "char",
  41  "int" or "bool" or the pointers to arbitrary objects, or "object arrays" which
  42  own the object pointers to which they store.
  43
  44  For the same portability reasons, the container classes implementation in wxWidgets
  45  does not use templates, but is rather based on C preprocessor i.e. is done with
  46  the macros: @e WX_DECLARE_LIST and @e WX_DEFINE_LIST for the linked
  47  lists and @e WX_DECLARE_ARRAY, @e WX_DECLARE_OBJARRAY and @e WX_DEFINE_OBJARRAY for
  48  the dynamic arrays.
  49
  50  The "DECLARE" macro declares a new container class containing the elements of
  51  given type and is needed for all three types of container classes: lists,
  52  arrays and objarrays. The "DEFINE" classes must be inserted in your program
  53  in a place where the @b full declaration of container element class is in scope
  54  (i.e. not just forward declaration), otherwise destructors of the container
  55  elements will not be called!
  56
  57  As array classes never delete the items they contain anyhow, there is
  58  no WX_DEFINE_ARRAY macro for them.
  59
  60  Examples of usage of these macros may be found in #wxList and #wxArray documentation.
  61
  62  Finally, wxWidgets predefines several commonly used container classes. wxList
  63  is defined for compatibility with previous versions as a list containing
  64  wxObjects and wxStringList as a list of C-style strings (char *), both of these
  65  classes are deprecated and should not be used in new programs. The following
  66  array classes are defined: wxArrayInt, wxArrayLong, wxArrayPtrVoid and
  67  wxArrayString. The first three store elements of corresponding types, but
  68  wxArrayString is somewhat special: it is an optimized version of wxArray which
  69  uses its knowledge about #wxString reference counting schema.
  70
  71 */