docs/latex/wx/tcontain.tex

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