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1 | \section{Container classes overview}\label{wxcontaineroverview} |
2 | ||
3 | Classes: \helpref{wxList}{wxlist}, \helpref{wxArray}{wxarray} | |
4 | ||
fc2171bd | 5 | wxWidgets uses itself several container classes including doubly-linked lists |
6e6110ee | 6 | and dynamic arrays (i.e. arrays which expand automatically when they become |
fc2171bd | 7 | full). For both historical and portability reasons wxWidgets does not |
6e6110ee | 8 | use STL which provides the standard implementation of many container classes in |
fc2171bd | 9 | C++. First of all, wxWidgets has existed since well before STL was written, and |
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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 | |
fc2171bd | 13 | will allow to base future versions of wxWidgets on STL - but this is not yet |
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14 | the case. |
15 | ||
fc2171bd | 16 | wxWidgets container classes don't pretend to be as powerful or full as STL |
6e6110ee | 17 | ones, but they are quite useful and may be compiled with absolutely any C++ |
fc2171bd | 18 | compiler. They're used internally by wxWidgets, but may, of course, be used in |
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19 | your programs as well if you wish. |
20 | ||
fc2171bd | 21 | The list classes in wxWidgets are doubly-linked lists which may either own the |
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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 | |
247aba10 | 24 | pointers depending on whether you called or not |
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25 | \helpref{wxList::DeleteContents}{wxlistdeletecontents} method. |
26 | ||
06ad8636 | 27 | Dynamic arrays resemble C arrays but with two important differences: they |
f70c0443 | 28 | provide run-time range checking in debug builds and they automatically expand |
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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 | ||
fc2171bd | 34 | For the same portability reasons, the container classes implementation in wxWidgets |
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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 | |
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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 | |
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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 | ||
06ad8636 | 47 | Examples of usage of these macros may be found in \helpref{wxList}{wxlist} and |
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48 | \helpref{wxArray}{wxarray} documentation. |
49 | ||
fc2171bd | 50 | Finally, wxWidgets predefines several commonly used container classes. wxList |
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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 |