f70c044346
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@29023 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
60 lines
3.4 KiB
TeX
60 lines
3.4 KiB
TeX
\section{Container classes overview}\label{wxcontaineroverview}
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Classes: \helpref{wxList}{wxlist}, \helpref{wxArray}{wxarray}
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wxWidgets uses itself several container classes including doubly-linked lists
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and dynamic arrays (i.e. arrays which expand automatically when they become
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full). For both historical and portability reasons wxWidgets does not
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use STL which provides the standard implementation of many container classes in
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C++. First of all, wxWidgets has existed since well before STL was written, and
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secondly we don't believe that today compilers can deal really well with all of
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STL classes (this is especially true for some less common platforms). Of
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course, the compilers are evolving quite rapidly and hopefully their progress
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will allow to base future versions of wxWidgets on STL - but this is not yet
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the case.
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wxWidgets container classes don't pretend to be as powerful or full as STL
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ones, but they are quite useful and may be compiled with absolutely any C++
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compiler. They're used internally by wxWidgets, but may, of course, be used in
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your programs as well if you wish.
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The list classes in wxWidgets are doubly-linked lists which may either own the
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objects they contain (meaning that the list deletes the object when it is
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removed from the list or the list itself is destroyed) or just store the
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pointers depending on whether you called or not
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\helpref{wxList::DeleteContents}{wxlistdeletecontents} method.
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Dynamic arrays resemble C arrays but with two important differences: they
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provide run-time range checking in debug builds and they automatically expand
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the allocated memory when there is no more space for new items. They come in
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two sorts: the "plain" arrays which store either built-in types such as "char",
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"int" or "bool" or the pointers to arbitrary objects, or "object arrays" which
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own the object pointers to which they store.
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For the same portability reasons, the container classes implementation in wxWidgets
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does not use templates, but is rather based on C preprocessor i.e. is done with
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the macros: {\it WX\_DECLARE\_LIST} and {\it WX\_DEFINE\_LIST} for the linked
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lists and {\it WX\_DECLARE\_ARRAY}, {\it WX\_DECLARE\_OBJARRAY} and {\it WX\_DEFINE\_OBJARRAY} for
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the dynamic arrays. The "DECLARE" macro declares a
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new container class containing the elements of given type and is needed for all
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three types of container classes: lists, arrays and objarrays. The "DEFINE"
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classes must be inserted in your program in a place where the {\bf full
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declaration of container element class is in scope} (i.e. not just forward
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declaration), otherwise destructors of the container elements will not be
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called! As array classes never delete the items they contain anyhow, there is
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no WX\_DEFINE\_ARRAY macro for them.
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Examples of usage of these macros may be found in \helpref{wxList}{wxlist} and
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\helpref{wxArray}{wxarray} documentation.
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Finally, wxWidgets predefines several commonly used container classes. wxList
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is defined for compatibility with previous versions as a list containing
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wxObjects and wxStringList as a list of C-style strings (char *), both of these
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classes are deprecated and should not be used in new programs. The following
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array classes are defined: wxArrayInt, wxArrayLong, wxArrayPtrVoid and
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wxArrayString. The first three store elements of corresponding types, but
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wxArrayString is somewhat special: it is an optimized version of wxArray which
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uses its knowledge about \helpref{wxString}{wxstring} reference counting
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schema.
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